NOT IDENTICAL!

False. Doctors know right away based on if they're in the same sac, or if they each have their own. If they're in the same one, they are identicle due to the fact that the egg split, and if they have their own, they are fraternal. If they call themselves identicle than they would have known by birth. They're egg could have split extremely early and may contribute the fact of why they don't look as similar as when eggs split late they have more physical attributes that are the same. It also doesn't help that one gained weight and the other didn't.