Why do my identical twins not look identical?

[Ratbag7]

They are 12 and I think each look quite unique, but they have recently been diagnosed as being identical twins through a DNA check. I read somewhere that “environmental factors” can sometimes mean that identical twins don’t look exactly identical. Anyone got any insight into this? Thanks

Can other people tell them apart if they have similar hairstyles/dress or is it just close family/friends who can?

I think it's quite common for close family/friends of identical twins to know them so well that you see the differences much more clearly and obviously whereas they look identical to others outside of that circle.

The environmental factors are things like height, build, and lifestyle - for example DS3 has a slightly triangular head, it was much clearer when he was a little baby and had less hair but I can see it really clearly, it's because I always held him in my left arm to feed (using my right arm to chase after his brother!) and coincidentally his cot was on the side of my bed facing the direction that caused him to lie on the same side of his head and it caused a slight flattening of his skull on one side. Nobody else can see this, even if I point it out to them. The doctor did see it when I pointed it out as a baby and he said try to encourage him to lie on the opposite side to balance it out, but it will round out by itself.

It isn’t just a case that you can see differences as you know them so well?

DS has identical twin best friends, now 16, friends since pre school. We can all tell them apart easily and wouldn’t say they are identical, but I reckon it’s just because we know them so well

My identical twins are ten. Definitely identical as shared a placenta. They don’t look the same although other people sometimes can’t tell and I’m a bit 🤔 one was 6ounces smaller and has maintained the difference she had always been shorter she is fussy with food, tended to be iller when little, needed steroids a few times duevto croup/ respiratory infections. Apparently this can inhibit growth less likely to finish her food. I find their hair really interesting as one has masses of thick hair, the smaller really fine. I’d say the environmental factors in our house are (slightly) poorer nutrition and medication when small.

I do think you are much more aware of the differences than everyone else.

Sometimes placentas can fuse, so sharing a placenta is not a guarantee that they are identical.

Could they be mirror twins. If you hold one up in the mirror do you see the other (so to speak). Apparently if they zygote splits that way it can happen (if so, you might want a scan to confirm where organs are as although it should all work fine there might be an issue in an emergency if they are a mirror!).

I think it’s fairly normal for close family to easily tell identical twins apart so it could be that they look more similar than you are giving them credit for or there could be other factors that mean they have grown slightly differently.

I am friends with 2 sets of identical twins, one set in their 40s and one in their 50s. They are obviously “identical” but if you know them you can easily distinguish between them. It’s people who don’t know them very well who tend to get them mixed up. I think there are always differences that can be seen if you actually know the people.

Mine each had am their own placenta. I only got the dna test as I was sick of people saying they were identical when I thought they were not and that the docs when they were born saying that they were not identical. Results came back with 20 lines of “identical”. They both have different faces, twin 1 looks more like my husband (and with the same personality to match) and twin 2 like me (with same personality to match).

I don’t think they are mirror twins

One of my best friends is an identical twin. I once found myself looking at facebook pictures and thinking, "wow they look similar". Haha. To me they now look completely different to each other, and I am surprised when I notice the similarities. I am 100% certain I woild never get them confused. To other people.... they cant tell the difference!

My dd went to school with a set that we so identical I literally couldn't say who was who with them standing in front of me. However now as late teens they have changed one looks like dad and one like mum It's crazy!!!

"I think it’s fairly normal for close family to easily tell identical twins apart"

Yes, if you know someone well you can distinguish them from their identical twin, but you can still usually tell they're identical!

So from a genetics point of view they have the same genes.

however they have had (slightly) different environments.

think about this example:
identical twins are born. One has a bad accident and his leg needs to be amputated.

it is now obvious which twin is which.

there are lots of environmental factors that affect how people look. For example, suppose one twin drinks more breast milk than the other. A small difference will result in the twins being (ever so slightly) different sizes.

maybe one twin catches chicken pox and gets some scars on his face but the other twin doesn’t catch it and so doesn’t have those scars.

and so on.

Depends when in the process they formed. When the fertilised egg split. The split can happen something like 2-13 days. A split at 2 days can even mean they have their own sac and placenta but not always. The later the split the more they look the same . Although all will share DNA. They early splitters will just not look so identical

So as Your’s had their own placenta they separated VERY early. So their environment was different from day 2-3. So it makes sense they don’t look perfectly identical

Two of my Aunts are identical twins (shared a placenta). Born just after WW2, my Granny didn't know she was having twins - the midwives hadn't picked it up. She already had three children. She knew something was wrong when "it didn't feel right" after the first was born and the midwives got a bit flustered and called a doctor.
The second, totally unexpected, twin was born shortly after and was quite small with breathing difficulties so was in intensive care for a few days. But, they are both now in their 70s. Even though they were identical, I've always been able to know which one was which since I was v. young. There are subtle differences in the face and mannerisms etc.

Thank you, that makes sense then, the reason why there are subtle differences. I wonder what the science is behind that, would be intriguing to find out!

They can still tell as when placentas fuse they get a bump at the join whereas monochorionic placentas are missing that twin peak. I had loads of scans checking the placenta that I think they’d of known. Could be wrong though!

I do wonder if there’s a bit of perception bias in there. My smaller twin shares a lot of personality traits with her older brother so I think I see the similarities there but I think it’s an expression thing posdibly? Or just seeing what you expect to see?

My identical twins are quite different. They shared a placenta. But one was so fidgety before he was born and still is. They have very different personalities too, and we suspect one may be autistic (we're awaiting diagnosis).

Environment can have a big effect on which genes are expressed and to what extent. Let's say both twins have the gene to produce exactly the same form of a particular hormone. But environment (even in utero) can affect how much of the hormone is produced. Which then affects how some part of them develops in the long term.

Our small town is bloody rife with twins, the last big twin day out we went on when ours were maybe 3 there was 136 twins there, they are now 11 so lots more new twins in the town! Our b/g twins have 3 sets of identical twins in their classes, only one pair look to me completely different. The rest I can guess based on hair style or football boot colour mostly!

I know two sets of identical twins and you can tell them apart quite easily (you know which one you are speaking too without asking if you see them separately) so I know what you mean. I can’t pinpoint what it is about them with one set that is different, but they really are identical but quite distinct, but the other set have different weights and slightly different face shapes.

I have a friend who is an identical twin. She has the same haircut as her twin.. I saw a photo of them both and had no problem picking out which one was her.

Another friend (X) has a supposedly non identical twin who they suspect is identical (different placentas and sacs but apparently this can happen with identical twins). I knew she had come to stay with X as X had mentioned it in the morning. I saw her in the afternoon. She had a tan as she had been on holiday, was 2 stone lighter than X and had a different haircut. I didn't think "oh that must be X's twin,' I thought 'oh X has had her hair cut.' Their identicalness (i know not a word transcended everything else) but if I had seen the two of them side by side I would have had no doubt which one was which.

OP can other people tell them apart easily? They will always look different you and close family.
My identical twins also didn’t share anything in utero and I was told, like you they wernt identical. Got them DNA tested as I was fed up of no one being able to tell them apart except us parents.
Mine look very similar to everyone else but different to me! The question I get asked most is ‘how can you tell them apart’ to which I always think- because they look very different!
I was curious when they were younger- if they share DNA, how come they arnt exactly the same- with the same strengths, weaknesses, likes and dislikes, same shape face etc. right from when they were born they had different personalities. It was explained to me like this: think of DNA as a bowl of cereal- everyone is a different cereal. Their cereal is Muslei- the same cereal but each bowl is different- one has more currants, one more nuts, one fewer oats etc.
Thats how it works with identical twins. Different variations of the exact same DNA. pretty fascinating when you look into it.

I was reading about a pair of twins today where one has primordial dwarfism, which is genetic, and the other doesn’t. The explanation given was mosacism.