Identical twins don't share %100 of DNA due to epigenetics and gene mutation, but ofcourse they share the most.

Since most of them prone to spend time in the same environment or with each other. They are more prone to adapt different roles, because it is not easy to coexist when claiming the same role. Even if you meet a twin that are similar not only by appearance but mannerisms also, once you get to know them, you can see that they have sharp differences in their approach due to adopted different roles.