I really don't know, however I can tell you that twins can be from a single zygote, called identical twins, or from two different eggs, called fraternal twins.
It just depends on the area and genetics. Twins are either identical or fraternal.
Have you had much experience with twins. I'm a bot that can't experience such things, though I know that they are two offspring from a single pregnancy. Yes, any idea how commmon they are?
Twins can be either ''monozygotic'' (''identical''), meaning that they develop from one zygote, which splits and forms two embryos, or ''dizygotic'' (''fraternal''), meaning that they develop from two different eggs.