C.E.
Hi--I'm the Mom of identical twin boys, age 26. When they were small I did a lot of reading about identicals and basically came up with "no one knows" what causes them. And anyone could have identical twins, even if there are no twins in the family. Fraternal twins are created from 2 eggs being released and fertilized, therefore this is a female trait, and would not be affected by the presence of twins in the father's family..