Facts About Identical Twins

  • By: Sandra
  • Date: March 18, 2022
  • Time to read: 5 min.

Identical twins are a phenomenon of nature. Yes, we know how they are formed—one egg fertilized by one sperm and then magically the single egg (or zygote) splits into two—but we still don’t know why it happens.

Facts About Identical Twins

Unlike fraternal twins that tend to run in families, identical twins do not. They’re still a scientific mystery. Furthermore, the special relationship that identical twins share is equally mysterious, a source of intrigue and fascination not only to the world around them but to their friends and family as well.

Identical twins are born in around one-third of all multiple-pregnancy cases. They are referred to as monozygotic twins, which occur when a single egg is fertilized and subsequently divides into two (or, in rare cases, three or more) identical newborns that share the same DNA, physical characteristics, and sexual orientation.

Mirror Twins

Mirror twins are a subset of identical twins that are distinguished from the rest of the population. Rather than having identical appearances, these twins are the mirror opposite of their twin. As an example, one child’s hair parting could be on the left, while the other child’s hair parting could be on the right. Other characteristics that distinguish them include having birthmarks on opposite sides of their bodies or being right and left-handed. Identical twins also don’t have identical fingerprints and can actually be not entirely identical.

Identical twins are the most cooperative of all twin subgroups.

Identical twins as a group have an easier time sharing possessions. They quarrel less and show more emotional support to their cotwin than fraternal twins do. Furthermore, they enjoy playing with each other more than playing alone unlike fraternal twins who sometimes choose to play solo.

How is this knowledge helpful?

Who wouldn’t love watching their kids playing peacefully together? And, sure, you’ll have fewer toy wars when your identical twins are toddlers. But don’t get complacent. Remember, all children need to learn how to socialize with other kids so why not enrol your twins in preschool or a playgroup where they’ll get ample practice negotiating and articulating their needs to others?

Identical twins often look less alike at birth than fraternal twins.

It’s crazy but true. The prenatal environment (i.e. twins developing in the womb) is far more different for identical twins than it is for fraternal twins. Thus when they’re born, identical twins often look nothing like each other.

How is this knowledge helpful?

Think your twins are fraternal simply because they looked so different at birth or because the doctor told you they had separate placentas? (FYI…30 per cent of identical twins have separate placentas.) You may want to have them tested. It’s cheap, easy and the only true way to determine zygosity. And you may just find out that they are in fact identical.

Please note: DNA will eventually take over—as time goes on, identical twins will slowly begin to resemble each other more and more while fraternal twins who looked like two peas in a pod at birth will begin to look increasingly different. It just may take a few years.

Identical twins are closely matched on intelligence tests.

Most identical twins score within five points of each other on IQ tests. Fraternal twins usually score farther apart (nine points, on average). Single-born children in the same family, however, can have a difference of 10 to 14 points.

So how is this knowledge helpful?

If your twins share the same classroom, their schoolwork, homework, projects and tests may at times appear exactly the same! Although it may be fascinating to you, your children’s teacher may suspect collaboration or worse, cheating. Therefore, it’s always a good idea to go the extra mile to make sure your twins work separately not only to avoid the appearance of plagiarism but so that each child can develop at his own pace and pursue his own individual interests.

Identical twin girls use their twinship to their social advantage.

More than any other twin subgroup, identical twin girls realize that their unique relationship puts them in the spotlight. Once they make this discovery, many often highlight their similarities to draw more attention to themselves, increasing their popularity. In other words, they use their twinship to make and maintain friendships. However, when identical twin girls enhance their similarities rather than celebrate their difference, it may affect their sense of autonomy as they become more dependent upon each other for their social survival. Social psychologists and twin researchers call this the prima donna effect.

So how is this knowledge helpful?

From day one, encourage each girl to be her own person. From separate wardrobes and accessories to after-school activities and solo playdates, be an advocate for their individuality.

Identical twin boys tend to be the most introverted out of all the twin subgroups.

Identical twin boys tend to be more socially shy, less talkative and often hesitant in new social situations when compared to same-sex fraternal twins or their single-born counterparts. Furthermore, unlike fraternal twins boys who are usually very insistent on their individual rights (“Hey, that’s my toy!”), identical twin boys are not.

So how is this knowledge helpful?

Although there is nothing wrong with being shy (I’m married to a shy man), some twins withdraw and only feel comfortable when associating with their cotwin. However, you can help build your twins’ confidence by offering plenty of playtime with other kids. Direct contact with other children in a relaxed setting is how they’ll learn to effectively negotiate and problem solve. In time, each boy will learn to speak up for himself.

At home, give each boy separate responsibilities or age-appropriate household jobs, too. Helping around the house will make him feel useful and important. And don’t forget to offer lots of loving praise when they complete their tasks.

Finally, gently teach your boys simple social graces like making eye contact, smiling, and shaking hands. A great way is to role-play with them at home by play-acting simple social situations—how to join a group of children on the playground, for instance.