Understanding the Different Types of Twins

By Angelita Williams

For the most part, when the majority of us think of twins, we think of identical twins and fraternal twins. While these two types of twins are by far the most common multiples we see, there are several other types of twins that exist within these categories. There are many misconceptions about multiples in the general public. Whether you are the parent of multiples, you have multiples somewhere within your family or friend group, or you are just hoping to start a family of your own, it is important to take an educated and straightforward look at the different types of multiples that occur. The following are the three primary types of multiples that can occur and then a description of several rare multiple types within these three primary categories:

Fraternal/Non-Identical Twins

Fraternal or dizygotic twins are commonly known as non-identical twins or dissimilar twins. These types of multiples occur when two fertilized eggs are implanted in the uterus wall at the same time. These eggs are fertilized independently of one another by two different sperm cells, but are both implanted in the uterus. These twins can be either both female, both male, or one female and one male. Essentially (at least scientifically speaking) fraternal twins are siblings that happen to share a birthday. Just as with any other siblings, fraternal twins have a very small chance of sharing a chromosome profile. These twins can look very similar or they can look very different from one another. Dizygotic twinning is determined solely by the mother. There is no scientific evidence that supports the father having any cause for the release of more than one egg from the mother. Fraternal twins are more common among older mothers, with cases doubling in mothers over the age of 35.

Monozygotic/Identical Twins

Monozygotic twins occur when a single egg is fertilized to form one zygote, which later divides to create two separate embryos. This process is believed to be a completely random and spontaneous event. The incidence of monozygotic twins is about three in every 1000 deliveries worldwide. Monozygotic twins are more commonly known as identical twins to the general public. These multiples are always the same sex and are almost genetically identical to one another. Interestingly, identical twins do not have the same fingerprints. Even within the small environment of the womb, people encounter different aspects of their environment, creating small differences and variations between them.

Semi-Identical Twins

This form of twinning is extremely rare, but is another type of twins that many people do not know about. Semi- or half-identical twins are twins that inherit the exact same genes from their mother, but different genes from their father. There is actually very little known about the science behind semi-identical twinning. For the most part, parents will not know if they have semi-identical twins or identical twins without having genetic testing performed.

By-line:

This guest post is contributed by Angelita Williams, who writes on the topics of online courses. She welcomes your comments at her email Id: angelita.williams7 @ gmail.com.

Ideas for Spending Separate Time with Your Twins

By Abigail Pogrebin

I’ve been asked often: How do we find a way to spend individual time with each twin when we know it’s so important? I know that the realities of life — the chaos of school, work, playdates, doctors’ appointments, errands, family events, neighborhood events, religious commitments, etc. — make it a genuine challenge to carve out separate time with twins. But since I feel so strongly (now that I have the benefit of hindsight) that each twin needs separate memories with parents, I suggest small rituals that can become routine. For example:

1. Take one twin to breakfast one morning a week — even if it’s just a muffin at a diner. Take the other twin to get a weekly hot cocoa (maybe you keep a survey of the best cocoa in town) or the best milkshake (depending on the season).

2. Have movie night once a month where you take one twin to a movie by him or herself or watch one at home — just you, your spouse, and one twin. Alternate months for each twin, or ideally, come up with another monthly date for the other twin.

CRUCIAL NOTE: YOU DON’T ALWAYS HAVE TO MAKE THE RITUALS OR EXCURSIONS THE SAME, AND IN FACT, THAT CAN DEFEAT THE PURPOSE, BECAUSE THEN THE RITUALS AREN’T UNIQUE ANYMORE, WHICH IS THE WHOLE POINT OF SEPARATE TIME. IS THERE A DANGER OF THE TWINS COMPARING OUTINGS OR TRADITIONS? YES, BUT THAT’S NOT SUCH A TERRIBLE THING, AND THAT’S NOT WHAT THEY’LL REMEMBER IN THE END.

3. Decide to have a “book group” with just one twin — so that you read the same book and discuss it in a kind of special, scheduled meeting over some treat. (As you can see, I encourage food rituals!)

4. Have a cooking or baking date once a month, or once every two weeks, when you choose a recipe to make together for the rest of the family.

5. Maybe have a weekly game of catch with one twin, or a weekly game of ping pong with the other.

The overall idea is to make some togetherness about just you and your twin (with or without your spouse). Obviously, it’s nice to try to tie the ritual to something your twin enjoys (and part of this discipline is that it will make you pay a little more attention to who each twin is — alone). The key is simply this: a little time together — on a regular basis — without the twosome. It’s not the norm — and it needn’t be — but a little singularity goes a long way to individuality, not to mention a more solid friendship with a twin’s folks. I welcome all questions about twins so please drop me a note: apogrebin@gmail.com.

ABOUT THE AUTHOR

Abigail Pogrebin, a Yale graduate and identical twin, is the author of One and the Same: My Life as an Identical Twin and What I’ve Learned about Everyone’s Struggle to Be Singular. Her previous book, Stars of David: Prominent Jews Talk about Being Jewish, went into eight hardcover printings. She began her career in broadcast journalism, producing for Fred W. Friendly, Charlie Rose, Bill Moyers, and then for six years at CBS News’ 60 Minutes, first as a producer for Ed Bradley, then for Mike Wallace. Segueing to print journalism after her two kids were born (and she wanted to travel less), she became a senior correspondent for Steven Brill’s Brill’s Content Magazine and a contributor to Tina Brown’s Talk Magazine. She has written for publications such as New York Magazine, the New York Times travel section, Harper’s Bazaar, Huffington Post, Good Housekeeping, Self, Parents, Salon, Tablet, The Forward, and Ladies’ Home Journal. She lives in Manhattan with her husband and two children. Visit her website at http://abigailpogrebin.com.