Twins that look different called

Fraternal twins & identical twins

About twins

We usually describe twins according to:

• how many eggs they develop from – 1 or 2
• whether they share a placenta in their mother’s womb.

The main types of twins are fraternal twins and identical twins.

Most twins are born healthy, but a twin pregnancy can mean a higher chance of health complications for you and your babies. If you're pregnant with twins, you and your babies will need extra check-ups.

Fraternal twins

All pregnancies start when a sperm fertilises an egg. This fertilised egg is called a zygote.

Sometimes a woman’s ovaries release 2 eggs, and a separate sperm fertilises each egg. This forms twins. These twins are called fraternal twins, dizygotic twins (meaning two zygotes) or non-identical twins.

During pregnancy, the developing babies get oxygen and food from their mother through the placentas and umbilical cords. Fraternal twins have separate placentas and umbilical cords. The technical name for this is dichorionic.

Fraternal twins can be the same or opposite sex and their genes are as different as any other brother and sister. Often, same-sex fraternal twins look different. For example, they might have different hair or eye colour. Occasionally they look quite similar.

Fraternal twins happen in about 70% of twin births in Australia.

Very rarely, fraternal twins share a placenta. These types of twins are called chimaeric twins.

Identical twins

Sometimes a fertilised egg splits within a few days of conception to produce genetically identical twins. Because these twins come from one zygote, they’re also known as monozygotic. Identical twins are the same sex.

There are 3 types of identical twins.

About one-third of identical twins split soon after fertilisation and form completely separate twins. Like fraternal twins, these twins have separate placentas.

The other two-thirds split after they attach to the wall of the womb. As a result, they share a placenta. The technical name for this is monochorionic.

In a very small number of identical twins, splitting might happen even later. In this case, both twins share an inner sac, called the amnion, in addition to sharing a placenta. The technical name for this is monoamniotic twins. They’re often called MoMo twins.

Identical twins happen in around 1 in 250 pregnancies in Australia.

Although identical twins have the same genes, they don’t always look the same. This is because children’s health and development are shaped not only by genes but also by experiences in the womb and after birth. For example, a twin who gets less blood from a shared placenta might weigh less at birth.

Sharing a placenta or inner sac: why it’s important to know

Sharing a placenta means that twins share a blood supply during pregnancy. Sometimes the blood supply is shared unequally, which can cause health problems for both twins.

Women who are pregnant with twins sharing a placenta need to be checked more often than women who are pregnant with twins with separate placentas. Frequent checks help to pick up any complications early.

Twins sharing an inner sac (monoamniotic) are also at a higher risk of complications during pregnancy because of the chance that their umbilical cords might tangle and cut off their blood supply. These twins are checked even more closely. Medical professionals often recommend that these twins are born at 32-34 weeks. This is earlier than other types of twins, who are generally born at 37-38 weeks.

Medical professionals use ultrasound to work out how many placentas twins have. The earlier the ultrasound, the more accurately it can say how many placentas there are. It gets harder to work out later in pregnancy. After the birth, medical staff will look at the placentas to check what type of twins they are.

Fraternal or identical: why it’s important to know

Same-sex twins with separate placentas can be fraternal or identical. For health reasons, it’s good to know whether your twins are fraternal or identical.

To find out whether twins are identical or fraternal, you can ask for a genetic test after your babies are born. This is called a zygosity test. The test doesn’t hurt and involves collecting a sample of cheek cells by rubbing the inside of your babies’ cheeks with a soft applicator (like a cotton bud). The cost of this test starts at $199 (for both twins) in Australia.

Identical twins are more likely than fraternal twins to get the same illness. If one of a pair of identical twins is diagnosed with a particular disease or health condition, like high blood pressure, the other twin should be checked often for early symptoms.

Because of their genetic make-up, identical twins will always be compatible for organ transplantation, if they ever need it. Fraternal twins are compatible only sometimes.

Other reasons why twins and parents of twins might want to know whether they’re fraternal or identical include:

• trying to work out the chance of having more twins in future pregnancies (only fraternal twins run in families)
• making sure they have the right information about their genetic make-up
• being able to answer questions from family, friends and others
• being involved in twin research
• just being curious!

Some identical twins are mirror twins – for example, their hair parts on opposite sides, they are oppositely handed, or they have birthmarks on opposite sides of their body. In some rare cases, their internal organs can be mirror images of each other. It’s not known why some twins are like this.

In very rare cases, twins can be born physically joined together in different ways. These twins, called conjoined twins (previously called Siamese twins), can happen if the fertilised egg splits quite late after fertilisation.

Triplets (1 in 5000 births) and quadruplets (less than 1 in 100 000 births) can develop as a result of combinations of fraternal and identical twinning. There are no reliable figures for quintuplets (5 babies) and sextuplets (6 babies).

More about twins

In Australia, twins happen in 1 in every 80 births. This means that 1 in 40 Australians is a twin.

The birth rate of identical twins is the same around the world and doesn’t vary with the mother’s age.

In contrast, the birth rate of fraternal twins varies widely across countries and can be influenced by the mother’s age. Women aged over 35 years are the most likely to have fraternal twins, because their ovaries are more likely to release more than one egg at a time.

More twins were born from the 1990s to the mid-2000s. This is because it was common to transfer more than one embryo during in-vitro fertilisation (IVF) treatments. The rate of twins from IVF is now lower, because it’s now usual practice to transfer only a single embryo.

Identical, Fraternal, and Other Unique Types

You may be familiar with the most common types of twins — fraternal and identical — but several other rare subtypes exist too.

More twins are born than you might think. As of 2019, the Centers for Disease Control and Prevention (CDC) reported that 32.1 out of every 1,000 births in the United States were twins. Read on for more details about twins.

The National Library of Medicine says that monozygotic, or identical, twins are conceived from one fertilized egg. This egg separates into two embryos after it has begun to divide. These two embryos develop into two babies.

Genetic materials called chromosomes in both babies are completely identical. This is because both babies come from the same egg and sperm. For this reason, both children are assigned the same sex at birth and share the same genetic characteristics, such as eye and hair color.

Still, because of differences in the environment where they’re born (like the amount of space each had in the uterus), identical twins may have slight differences in appearance.

Not all twins are identical, of course. More often than not, twins are born with unique physical characteristics. Nonidentical twins are generally known as fraternal twins.

Fraternal twins

The scientific term for fraternal twins — “dizygotic” — refers to two fertilized eggs. Dizygotic twins happen when the birthing parent’s body releases two eggs at the same time. A different sperm will fertilize each egg.

Since fraternal twins are the result of different eggs and different sperm, they share the same percentage of chromosomes as any other siblings. The National Human Genome Research Institute says that this is about 50 percent. This is why they don’t look exactly alike and can be assigned different sexes at birth.

Traditionally, the science around twins has taught that identical and fraternal are the only two types. But a third type might exist, called polar body or half-identical twins.

Though this has never been confirmed, a research review from 2016 suggested that a third twin type would explain why some fraternal twins look so similar.

After the ovaries release an egg, the egg can split into two halves, the smaller of which is called a polar body. This polar body contains all the chromosomes necessary to join with a sperm to create a baby. But since it usually contains very little fluid, or cytoplasm, it’s often too small to survive.

It’s possible, though, that a polar body could survive and be fertilized. Meanwhile, the larger half of the original egg could also be fertilized by a separate sperm. The result? Polar twins.

Polar twins share the same chromosomes from their birthing parent, but they get different chromosomes from their non-birthing parent. This is because they’re created from a single egg but two separate sperm.

For this reason, they may or may not be assigned the same sex at birth, and they may look very similar but not exactly identical.

In a basic twin pregnancy, two embryos go their separate ways and develop into twin babies, whether identical or fraternal. Some unique sets of twins follow a different path.

Mirror twins

Mirror twins are exactly what they sound like! These twins are actual mirror images of each other. This means that:

• Their hair may naturally fall in opposite directions.
• Their teeth may grow in on opposite sides of their mouths.
• They may have birthmarks on the opposite side of their bodies.
• They also usually have different dominant hands.

What causes this phenomenon? In a typical identical twin pregnancy, an egg splits during its first week after fertilization. But in a mirror twin pregnancy, the egg splits 7 to 12 days after it’s been fertilized — long enough for the egg to have developed a right and a left side.

Conjoined twins

Conjoined twins are a rare twin type in which the two siblings are physically connected. Typically, conjoined twins are joined together at the chest or abdomen, but this varies. Some conjoined twins are connected to a greater extent than others. Most share at least one vital organ.

Though physically attached to each other, conjoined twins are two individuals. They have unique thoughts and their own personalities.

Researchers are still trying to understand the origins of this type of twin birth. Some experts believe conjoined twins occur when a fertilized egg doesn’t split completely. This happens when the egg divides 12 or more days after conception. Another theory is that the fertilized egg divides completely, but it later fuses back together.

A conjoined twin pregnancy is high-risk, but breakthroughs in surgery have been able to improve outcomes. Surgery can even allow conjoined twins to live independently. Although a small 2011 study found that just 7.5 percent of conjoined twins live past birth, advances in care for conjoined twins are being made every year.

Parasitic twins

Sometimes, as twins develop in utero, one twin becomes larger and more dominant. The other twin stops developing and begins to depend on their sibling. Known as parasitic twins, these twins are physically conjoined.

However, the smaller twin is not fully formed and isn’t capable of surviving on their own. This is because the smaller twin is usually missing vital organs or a fully developed brain or heart.

In fact, you might not even recognize the smaller twin as a separate individual. This “twin” may appear on the sibling’s body as a small lump, extra limbs, or a second non-functioning head.

Parasitic twins may be classified into subtypes, including fetus in fetu and acardiac twins:

• Fetus in fetu. These are rare circumstances when a smaller twin develops inside the larger twin’s body.
• Acardiac twins. In this case, one twin receives too much blood flow while the other doesn’t receive enough. This occurs because identical twins share a placenta.

A milder version of this is called twin to twin transfusion syndrome (TTTS). Acardiac twins experience a more extreme form of TTTS that may result in developmental issues for the fetuses. Treatments like surgery can improve outcomes, according to 2015 research.

Semi-identical twins

There have only been two reported cases of semi-identical twins, so this type is extremely rare.

In semi-identical twins, two separate sperm fertilize one egg. The fertilized egg then splits in two. So, semi-identical twins share all the same chromosomes from their birthing parent, but only about 50 percent from their non-birthing parent.

Female and male identical twins

Sometimes identical twins can be assigned the sex of male and female at birth. These twins start off as identical males with XY sex chromosomes. But shortly after the egg divides, a genetic mutation called Turner syndrome occurs, leaving one twin with the chromosomes X0.

This twin will be assigned female at birth but may have developmental issues, as well as difficulties with fertility later in life, according to the National Health Service. The mutation doesn’t affect the other twin, who is assigned male at birth.

Twins with different ages

Once a person becomes pregnant, their body stops releasing new eggs for potential fertilization — except in some rare cases.

A phenomenon known as superfetation can occur when a second egg gets released and fertilized after a person is already pregnant. When this happens twice within one menstrual cycle, it’s known as superfecundation.

In this case, both fertilized eggs will develop, but one twin will be slightly older than the other.

Twins with different fathers

If two eggs are released within a single menstrual cycle, it’s possible for them to be fertilized by sperm from two different people.

This is known as heteropaternal superfecundation — a common occurrence in animals but very rare in people.

Twins with different skin colors

It’s very unlikely to have twins with different skin tones, but it can happen in three different ways:

• When parents are of different complexions, one of their fraternal twins may naturally resemble one parent, while the other twin looks more like the other parent.
• In the rare case of heteropaternal superfecundation, the two non-birthing parents may have different skin tones. Each twin would then receive that person’s genetics.
• When both parents are biracial, this usually results in twins that both look biracial. Occasionally, though, each twin may receive more genetic material from different ancestors than the other. This can lead to the twins appearing to be from different “races.”

Twin pregnancies often come with an increased risk of developing some medical conditions. These can include:

• Placenta previa. In placenta previa, the placenta sits too low in the uterus, covering the cervix.
• Placental abruption. With placental abruption, the placenta detaches from the uterine wall, causing bleeding, back pain, and abdominal tenderness.
• Placenta accreta. The placenta attaches too deeply into the uterine wall when placenta accreta occurs.
• Prematurity. A premature baby is one who is born before 37 weeks of pregnancy.
• Low birth weight. A baby with low birth weight is born with a weight that’s less than 5 pounds and 8 ounces.
• Gestational diabetes. In gestational diabetes, the birthing parent’s blood sugar is too high during pregnancy.
• Gestational hypertension. In gestational hypertension, the birthing parent’s blood pressure is too high during pregnancy.
• Postpartum hemorrhage. When a postpartum hemorrhage occurs, the birthing parent experiences heavy bleeding after delivery, often because of an undelivered placenta or the uterus not contracting properly.

Most twins are fraternal or identical, but a third type, polar body twins, might exist too.

Some other subtypes exist, but these are extremely rare. Many occur under unusual circumstances.

A twin pregnancy has risks of complications, so parents should make sure to receive good prenatal care and seek medical attention for any concerns.

how science studies twins and twins - Knife

Multiple pregnancy is different. In one case, two children may be born, and in another, for example, six. But much more interesting for biologists is the "qualitative" rather than the quantitative characteristic of this phenomenon, so first let's deal with the terms that many confuse.

Twins grow together in the womb and are born on the same day. They can be mono- and dizygotic, which are also often called twins . Such embryos are formed as a result of the fertilization of two mother's eggs by spermatozoa. They can be both same-sex and different-sex, they can have a similar appearance and character - or, conversely, completely different.

Monozygotic siblings are the result of fertilization of one egg by a sperm cell. Previously, scientists believed that the set of genes in such people is identical and, accordingly, they are like each other in every way like two drops of water: appearance, interests, behavior, etc.

It is also believed that monozygotic twins, due to their genetic makeup, cannot be of opposite sex. And in most cases it is really two boys or two girls. But there are also semi-identical brothers and sisters who share 100% of maternal genes and, for example, 78% of paternal ones. nine0003

In addition, external factors, such as nutrition, the stress of a woman in labor, etc., also affect a person’s development. Alessandra Piontelli, a neuropsychiatrist and author of the book “Twins: From Fetus to Child,” found out that they can change the conditions of the intrauterine environment. And then, for example, one of the monozygotic siblings will receive more nutrients than his brother or sister, which will affect their physical condition (say, the first baby will be born larger) and behavior. And Manel Esteller of the National Cancer Center in Madrid found that as twins mature, mismatches in the epigenome accumulate. For example, the less time they spend together, the more differences between them. nine0003

See also

How does parental nutrition affect their unborn children?

However, in society, identical siblings are most often treated as natural clones with identical genetic makeup. It is believed that not only between monozygotic twins with the same appearance, but also between completely dissimilar twins, there is a mystical inseparable connection.

This stereotype is rooted in ancient myths about Apollo and Artemis, Hercules and Iphicles, Romulus and Remus. Then they believed that the twins are an indivisible whole, they feel each other at a distance and are able to exchange thoughts almost telepathically. Divine fetters bound even the eternal antagonists who grew up in the same womb. nine0003

A special attitude towards twins persists even today - remember at least films about sisters and brothers - pranksters, identical down jackets and hats, and the names Masha and Dasha, barely distinguishable by ear. Almost identical people attract everyone's attention to themselves, and their ideal relationship is envied, because everyone wants to have a person nearby who will understand him one hundred percent and stay with him forever.

Strategies for raising twins and twins have developed under the influence of this legend. First of all, dressing children in identical outfits is a fun practice that helps to collect likes on Instagram. And later, the observance of this ritual can also bring fame (tiktok twins Katya and Nastya have 5.1 million followers). Secondly, buying the same toys, taking very similar children to the same circles, and generally treating them as one person is easier and less energy-intensive. nine0003

Fitness twins Liza and Nastya were raised in this way. Throughout their childhood, they were inseparable: they sat at a desk together, went to dances and carried one set of textbooks for two. Mom and dad considered them to be a single entity, called them not by their names, but simply “daughters”, scolded and praised both of them, regardless of which of them excelled.

But 22-year-old Anya and Tanya Grin, who had a similar childhood, did not like this equalization. The girls' parents worked hard, and their time and love was only enough to ensure that the basic needs of their daughters were met. So Anya and Tanya entertained each other and tried to be obedient. And when they grew up, they decided that they would be as different people as possible, so that they would finally stop being compared.

The Grin sisters had to endure many quarrels and whole months of silence before each of them got rid of her doubts and began to realize herself as a separate person. To avoid such a scenario, modern child psychologists are increasingly saying that any siblings should be initially perceived as different people. nine0003

For example, Sergei Malykh, head of the laboratory of age-related psychogenetics at the Psychological Institute of the Russian Academy of Education, advises in the book “I or WE: How to Raise Twins”: behaved in the same way, they often react negatively to various kinds of "deviations" from this "standard". As a result, the child develops a whole bunch of psychological problems: from a neurotic attempt to prove to mom and dad that he can be loved like that, to a defeated self-esteem, because he is “not good enough.” nine0003

The mother of 6-year-old Arseniy and Prokhor Olga carefully prepared for the appearance of twins: she subscribed to thematic blogs, read books, and even before their birth she knew that she would encourage the difference between brothers. And yet, she took the grown-up boys to football in the hope that both of them would like this activity: “Arseny spent the whole game picking the net on the gate with his finger, and Prokhor ran and had fun. Of course, one section is a breath of freedom for parents. But I realized that Arseny would suffer, and he no longer goes to football, but studies with a tutor while Prokhor is chasing the ball. It’s difficult, but it’s better to suffer than to hear complaints from children about you later.” nine0003

Olga knew that comparing brothers could harm their psyche, but she still set one as an example to the other, because she wanted Arseniy to be as obedient as Prokhor.

Mom took him to see a psychologist, where it turned out that all this time the boy wanted to attract the attention of his parents and show them that he was cooler than his brother: “There were toys on the table, and the psychologist asked Arseniy to choose the members of our family. He found dad - a mustachioed demon with a weapon, me - little Masha, a big and strong himself and a microscopic brother. At that moment, I realized that Arseniy wanted to be better than Prokhor, because I always compared him with him - and made a huge mistake. Now we began to pay more attention to him, we often say how cool he is. And right before our eyes, the child has changed a lot: earlier, Arseny did not allow himself to be kissed and immediately wiped himself off, he never expressed his feelings for us, and now every five minutes he repeats: “Mommy, I love you.” nine0003

In addition to psychological problems, twins sometimes have developmental difficulties, adds Nikita Karpov: it is so important to socialize the twins, and preferably separately.”

The same advice is given by the Soviet and Russian psychologist Nina Talyzina in the book "The Nature of Individual Differences: An Experience in Twin Research":

It is very important that parents, despite household chores, communicate with their children more often, talk to them in “normal” speech, read books, tell fairy tales. ”

Arseniy and Prokhor's mother claims that they don't need friends: "They always find something to do: they either fight or play war games, hide and seek - and at school they hang out together, that's a big plus." nine0003

But there are also disadvantages. First, Olga notices that the socialization of the brothers is slower than that of their peers. The boys have no one to invite to their birthday. Secondly, mom constantly reminds the more active Prokhor not to leave Arseny and pull him along to play with other children. And to shift the responsibility for the emotional state of one child to another, according to her, is wrong, but so far this is the only way.

Adult twins and twins who are too close are also often told that this is an unhealthy relationship. Renowned pediatrician Benjamin Spock wrote: “...everyone likes it when twins dress the same and look the same. <...> It is really a charming sight at 3 years old. But if, as sometimes happens, the twins are still trying to attract attention with their resemblance and dress the same way even at 30 years old and are so dependent on each other that they are not able to fall in love or start a family, then the result is not charming, but very sad. nine0003

The negative evaluation of strong twin attachment is also associated with the condemnation of any form of addiction and abuse in the self-help culture. Addiction is a disease that needs to be constantly monitored with the help of special tests, and if detected, it must be dealt with by psychotherapy methods.

The prevailing view in modern research is that the relationship between twins is pathological in nature. A number of scientific works have shown that "co-dependent" members of related couples, who, together with the cradle, are prone to alcoholism, narcissism and neuroses. nine0003

Therefore, psychologist Joan Friedman advises adult twins not to put their relationship with their brother or sister at the forefront and choose other priorities in life. Otherwise, they will face an identity crisis, which can manifest itself if, for example, one of them moves to another country. Separated by distance, the twins will not know who they really are or what they want.

When Nastya moved to Moscow, and Liza remained in her hometown, the most difficult period in their life began. They were constantly in touch, could not sleep and eat normally. As a result, after three months, Liza also moved to the capital. nine0003

Most twins are actually attached to their sibling. This was found out by psychologists from the University of California. In their analysis, they relied on the theory of psychiatrist John Bowlby, according to which a secure type of attachment is formed in an infant when the mother is attentive to his needs and fully satisfies them. If the child begins to understand that the mother will always give him what the baby needs, over time he will be able to do without her constant presence. nine0003

But Bowlby did not take into account the specifics of families with two or more children. This difference is explained by Joan Friedman in Emotionally Healthy Twins. Firstly, the baby is never left alone - there is always someone very similar to him with him. And secondly, they are constantly fighting for the resource, and someone has to wait for the mother's answer while she is busy with another child. So the first baby can form an anxious type of attachment with his mother and a reliable one with his brother or sister. But the psychologist notes that the latter will never replace the connection with the main guardian, who is older and wiser and able to help find his individuality. Therefore, Friedman advises parents to try to create a strong bonding with two children. nine0003

The researcher also notes that twins often face a problem when one of them takes care of the other, that is, takes a dominant position, and the second is in a subordinate position. In such a situation, the expert advises to work on his own self-esteem, so that the person understands that he can quite cope without his brother or sister. And the caring twin must realize that his love for the sibling will not weaken if he does not constantly run to help him.

"An independent person makes decisions on his own, instead of relying on a twin who is always ready to lend a shoulder - and knows how to take care of a brother or sister without being too close to them. Excessive emotional attachment leads to overprotection, which leads to unhealthy addiction, ”writes Friedman.

The third trap that the psychologist says twins often fall into is the "love-hate dynamic."

Genetically identical people find it difficult to accept their negative emotions towards each other, because they believe that they must "match" in everything. nine0016

Some twins find it difficult to express any feelings other than those of their brother or sister. Anya and Tanya, for example, were forbidden by their parents to argue, because "they are the closest people", and then the girls themselves could no longer enter into discussions with each other. Friedman believes that an important step towards achieving personal independence for each twin is the recognition of the "secret struggle" between them.

Trying to be yourself

Anya Grin graduated from the Faculty of Psychology and understands what Joan Friedman writes about. The girl admits that all her life she tried to artificially separate from Tanya and show everyone that she is different, despite the outward resemblance to a twin. nine0003

“There was a period when I did not accept the views, thoughts and world of my sister. I didn’t want to introduce her to my new friends so that they wouldn’t compare us, I was afraid that against the background of Tanya I wouldn’t be so cool anymore. She was jealous of our mutual friends. At some point, it even seemed to me that people were interested in me only because of my sister, because she was always smarter, more beautiful and more fun. Since 15 years, we have developed completely different companies, we did not really come into contact with each other.

Now I realize who I am and who my sister is. All my friends also see how different we are with her. I have been going to this all my life and finally reached the goal.” nine0003

Nikita Karpov believes that it is more difficult for twins living in a situation of “sameness” to express their own desires, which means that they will need more time to discover and understand themselves.

Sisters Nastya and Liza do not know what each of them likes individually. “We make all decisions collectively. Liza never thought about what Nastya likes, and vice versa. If something is to the liking of one, then the second will also be OK, ”the girls say, and this lifestyle suits them completely. nine0003

However, Nastya and Liza admit that there are also disadvantages. They share all the responsibilities: while one cooks food or conducts serious negotiations, the second develops a training program or responds to comments on Instagram.

But if one of them leaves, the other falls into a slight stupor and does not know what to do. It takes several days to adapt to new realities.

Such a relationship interferes with girls in their personal lives as well. Previously, separation was difficult for the sisters and they tried to spend every evening together. Therefore, their husbands were indignant: "Can you at least one day be without each other?" But now Nastya and Liza understood the desires of their spouses and began to negotiate who and when spends time separately with her husband or goes on vacation. nine0003

I am We

“We depend on each other, but this is our strength, uniqueness and individuality. We like to constantly hear that we are the same, many ask to take a picture with us. Due to the fact that we are very close, we are never visited by depressive thoughts, we are not lonely, ”Nastya and Liza list the advantages of their affection.

Anthropologist Dona Davies, author of Twins Talk, did a study with her twin sister and found that many identical siblings have a more subtle sense of their uniqueness compared to other people: “Each twin enriches both himself and the other. A similar dynamic can emerge in a family where two people retain their individuality while at the same time enjoying the joys of living together and needing a spouse. But if such reciprocity in marriage indicates a healthy relationship in a couple, then in twins it, unfortunately, is considered dysfunctional. nine0003

Vladimir Semyonov, candidate of psychological sciences, expresses a similar idea: “Common experiences bring twins even closer and, to some extent, expand their possibilities of self-knowledge. In those couples between whose members there is a strong interdependence, the concept of "I" is inseparable from the concept of "We".

Anya and Tanya, Liza and Nastya, as adults, learned to communicate again. 20-year-old girls began to feel personal boundaries and respect each other's wishes. At the same time, Anya often sacrifices her needs for the sake of her sister - for example, she can take over her work, even if she does not have time or she is very tired. In such situations, our interlocutor is looking for a positive and is always ready to help Tanya. nine0003

“I think that 9 months spent with a person in one stomach still means something,” Anya thinks and adds that she would not change anything in her life if such an opportunity arose.

Did you know? How twins differ from twins

It would seem, well, what's the difference: they were born at the same time, which means they are twins, but no. It is possible that they are twins. Let's try to figure out what the differences are.

Do you remember that old issue of Yeralash, when the brothers nearly drove a passerby crazy trying to explain to him that they weren't twins? “But you are brothers? Brothers. Birthday on the same day? Into one. So twins." There it turned out that there was also a third - triplets. But there is, it turns out, a fundamental difference between twins and twins. nine0003

So what is the main difference? In medical terminology, the concepts of identical and fraternal twins are used. Twins are two or more children who grew up together in the womb and were born at almost the same time. Fraternal twins are commonly referred to as twins, and identical twins are simply called twins.

Here's what makes them different:

* Twins can be of the same sex or different sexes. But twins are always same-sex.

* Twins are always identical. They are very difficult to distinguish externally, especially to strangers. They have the same blood type, the same diseases and complete portrait resemblance. And the twins look like siblings, as if they were born to the same mother, but at different times.

* Twins are born about 1 time in 4 thousand births. Twins are more common, once per 1000 births.

* To conceive twins, only one egg is needed, and twins need 2 different eggs. nine0003

* In vitro conception increases the chance of having twins. Also, the likelihood of having twins increases in women who take hormonal contraceptives for a long time before conception.

Twins are born from a single egg, which requires only one sperm to be fertilized. Then it, for reasons unknown to science, is divided into two parts. As a result, genetic copies are formed. Each of the cells will develop into an independent embryo.

A visible distinguishing feature of already born babies is their "similarity" to each other. Twins are always alike, twins are not. From a medical point of view, things are a little more complicated. In medicine, there is no concept of twins and twins, there are concepts of monochorionic and dichorial twins. The difference is in how fertilization occurs. nine0003

Dichorionic twins are expressed in the fact that each embryo forms its own placenta and amniotic sac, therefore, each of the babies has its own place in the womb and feeds from its own placenta. From a medical point of view, this is more favorable for the birth of healthy babies.

In monochorionic twins, both embryos develop in the same embryo sac and always have a common placenta, which, in some cases, makes pregnancy difficult and a number of complications occur. nine0003

Monochorionic twins are often genetically identical, of the same sex and very similar to each other, they are called twins. As for dichorionic twins, here babies can be both same-sex and different-sex, and do not look alike in any way.

Twins develop from two eggs fertilized by sperm. They may even have different fathers. This is due to the fact that in rare cases, when a woman ovulates, two eggs are released from the ovary, although usually only one is released. For this reason, fraternal twins or twins are born in the family. nine0003

So, twins are natural clones who have identical appearance, character and even hereditary diseases. They cannot be of different genders. And twins are brothers or sisters or brother and sister who have similarities and differences, as if they were not born at the same time, but as a result of different pregnancies from the same mother.

Scientists at the University of Washington conducted a series of studies on the life span of identical twins.

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