Once you have twins, it’s amazing how many people come out of nowhere to tell you about the twins in their families. People you’ve never even seen before, much less talked to, suddenly appear over your stroller whenever you’re out, cooing over your babies and telling you all about their twin nieces/siblings/kids/parents.
A lot of what comes out of these people’s mouths is scientifically impossible. Myths about twins abound and I used to believe many of them myself, until I found out I was pregnant with twins close to 12 years ago and decided to do some research.
So, for those seemingly very few of you who don’t have twins in your family, and for those who do but are unclear about the ins and outs of twindom, here are a few basic myths debunked for you.
1. All twins look the same. This is one I always thought was true. To me, the word “twin” was synonymous with “look-alike” and I’d always look for similarities between the twins I knew, thinking they must look at least somewhat alike, if not exactly alike.
The truth is, fraternal twins may or may not look similar, no more so than regular siblings. What can throw people off is the fact that they’re both in the same stage at the same time, so if they do look even somewhat alike, it can be difficult to tell them apart if they’re the same gender.
This is true of my twin nephews, who by all hypotheses and evidence are fraternal twins. I can’t tell them apart very well at all and only people who are with them a lot can. There are differences if you stop to look, but they look pretty identical to me. Now that they’re 4-1/2, they like to play the “I’m-Twin-A-(But-I’m-really-Twin-B)” game.
2. Twins show up “every-other generation” and can come from the father’s side of the family. I never heard this until I had twins myself, but I can’t tell you how many family members told me that I was probably having twins because they were in my husband’s family two generations ago. This was an even more popular theory when people found out that I have no twins in my family at all. “Twins skip a generation,” I heard over and over.
Nope, this is simply not the case, unless it’s purely coincidental. First of all, identical twins don’t “run” in families at all. They are simply a miracle of nature, somehow splitting early on from one baby into two. Identicals are much more rare, completely random and extremely fascinating. Fraternal twins do tend to be genetic, but only on the mother’s side. Why? Because fraternals are the result of two different fertilized eggs, rather than just one egg and one sperm that has split into two, so the tendency to produce more than one egg at a time run in the family. The reason why it may seem that twins skip a generation could be because moms pass on the gene to “hyperovulate” to their sons, who then pass it on to their daughters, resulting in twins in the third generation rather than the second.
3. You can tell just by looking whether or not twins are identical or fraternal. While identical twins do generally look very similar, as mentioned before, so can fraternal twins. Other factors such as environment, development and personal preferences can cause even identical twins to look different or fraternal twins to look more similar. There are plenty of twins out there who don’t know for sure whether or not they are fraternal or identical, so being able to judge this simply by looking is impossible.
The only time you can know for sure that a set of twins is fraternal just by looking is if they are boy-girl twins. Because they are different genders, they have to come from two separate eggs.
4. In terms of personality, twins are either completely opposite or exactly alike. I know, this seems like a “duh!” one to me too, but stories and legends throughout history have perpetuated this myth of one “good” twin and one “bad” twin, or one leader and one follower. As with any other child, this completely depends on personality. Obviously parents of twins should take great care to let each one develop into her own person with no expectations or relegated roles, whether the two end up having similar personalities and interests or not.
My twins are very different personality-wise, for the most part. I wouldn’t categorize them as a leader and a follower, but one of them is very outgoing and extroverted, while the other is more reserved and introverted. They do share similar traits in terms of their scholastic abilities (both get nearly identical grades ), musical and artistic abilities and their overall character traits (kind, sweet, thoughtful, loving), but except for the fact that they were born within 5 minutes of each other, they could be just regular sisters.
There are other myths out there in terms of raising and caring for twins too, everything from “you can’t breastfeed twins” to “twins must be separated in school.” I’ll be going into those more another time.
Have you believed any of these myths? What is the most surprising thing you have learned about twins, either in the past or from this post?
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Yeah, my husband is a twin, and he and his brother look the least alike of the four of them.
I know another set of (adult) twins who are in the “are they identical or are they not?” category, but I think I’ve figured out the answer. In reading a book called “The GenoType Diet,” the author discusses “epigenetics” — which is basically, how your fetal environment molds and shapes you in your mother’s womb, to work “above” mere genetics to make you unique. Even though twins share the same womb environment, they may respond to stress differently, or somehow one twin may get more of one nutrient or be subject to more stress than the other twin. [My husband stole the lion's share of iron, and he was much darker than his brother at birth, and has remained darker than the other 3 brothers, too, fwiw.] This is why even identical twins have different fingerprints — if it were merely genetics, and they had identical genetics, they should have precisely the same fingerprint pattern, but they don’t. Some identical twins are mirror images of each other (one right-handed, the other left-handed, e.g.).
So, back to the possible identical twins I know — I think they are identical — when they were teenagers, the only way I could tell the difference was that one parted his hair down the middle and the other parted his hair on the side. Knowing them better now, I can easily tell the difference between them (since one of them is slightly heavier than the other, that helps), but back then it was almost impossible. Occasionally now I still do double-takes.
Now on the “fwiw” note — monoamniotic-monochorionic (MoMo) twins are always identical — these are babies that share the same amniotic sac during pregnancy. Identical twins can also have separate amniotic sacs. (I think the difference depends on when the single fertilized egg split into two people — probably, the earlier split leads to separate everything, while the later split leads to joined everything; conjoined twins obviously are the latest split, and split incompletely.) Fraternal twins obviously never share the same amniotic sac, but many times the placentas merge together. So, if after the babies are born, there is only one amniotic sac in the afterbirth, you can tell that the babies are definitely identical without a genetics test. Pretty cool, I think.
Yep, I know all about the amniotic sac thing too. The doc thought my twins were identical before they were born. Once they were out though, it was clear that they were in no way, shape or form identical. Part of why he thought they were is because it looked like there was only one placenta. However, after they were born, he found that their placentas had fused together, so clearly they were fraternal.
While doing research for this post, I ran across some scientific evidence about twins that can actually be identical and different genders. It was very fascinating, but much too technical for this blog and besides, it’s so rare as to be virtually unheard of. So I decided not to go there. =) It needs its own separate post.
Love your article!
There are plenty of twins in my family. My mother is a fraternal twin and two of my uncles on my mom side are fraternal twins. On my husband side, he has 2 cousins who are fraternal twins.
I have always wonder if I was genetically predisposed to have twins myself and your article make me wonder…
My maternal grand-mother could have passed me the genes but my husband genes not what will affect my eggs! ;o)
Thank you for the tips!
Oh and you have an error in your post… I think you wanted to say “You CAN’T tell just by looking…”