Fraternal twins do, identical twins do not. Fraternal twins run in the mother's family, whose women sometimes release more than one egg at a time, and when both are subsequently fertilized by separate sperm cells.
Identical twins occur when a single fertilized egg splits into two parts. Depending on how late that happens, you can get "mirror twins", or even conjoined/Siamese twins.
My granddaughters are mirror twins, one looks to be left handed, the other right handed. Their hair swirls in oppossite directions. I still can't always tell them appart in photos even when both are in the photo. One in a photo? Fuggit about it. One in person, usually I can tell. Both together, in person, I can almost always tell. And they are actually quite a bit different in size, one weighs 3-4 pounds more and is an inch taller, and that's a lot when the lighter one only weighs about 21 pounds. :)
Thanks. Did you see my post above? Interesting about the proposed third type of twin but they info did not say whether the 3rd type runs in families like fraternal or it is like identical and is haphazard.
This poor woman had her babies taken from her because she failed a DNA test, but they tested the wrong part of her body and she would produce two different DNA results depending on which area was tested.
I have boy/girl twins, now 18 years old (miracles of modern science). I recall often being asked if they were identical— they look NOTHING alike, and we didn’t dress them alike. Our stock response was that our daughter’s penis was slightly larger than our son’s....