Ugh... I have to say this. Or else.
Twins are (almost) identical only if they are both girls or both boys. If they are a girl and a boy, they can be as similar as two non-twin siblings. That's because "identical" twins come from a split ovule (that is, same DNA: same chromosomes XX or same chromosomes XY) and non-identical twins come from two different ovules (different DNA; could be two girls, two boys, or girl and boy).
This is not hidden information. People learn this at primary school. So why why why do writers, mangakas, film makers, why do they omit this fact? I don't buy they ignore this!
aah now that I have let off steam I feel I am open to read any nonsense.
Actually, it all depends on your genetics. My brother and I, for example, are five years apart in age and different genders, and we look nearly identical. It's only small differences (like he's a little taller than me and has bright blue eyes, rather than my grey-blue ones) and genitalia that separate us. And I look the same as my mother, grandmother, and great grandmother. That side of my family just has really dominant genes. So, it all depends really. Twins can can look as different or similar as can be. =]
last edited at Nov 16, 2013 4:21PM