Quote Originally Posted by Toby's my baby
I'm actually not quite sure on what makes you fraternal and identical. It has nothing to do with what you look like, I think it is have one "sac" or two...??

Identical twins come from one egg, that's split in two. Therefore you come from one sac.

Fraternal twins are two eggs that are fertilized at the same time, so you'll have two sacs.

Hoped that helped!