How can one have identical twins?

There are two primary types of twins, Identical and Fraternal.

Identical twins occur when the egg splits after fertilization. To date no indication of a genetic link has been found. Anyone has a chance, though small, of having identical twins.

Fraternal twins occur when more than one egg is dropped during ovulation. This trait can be inherited from the mother's side of the family. Studies have shown that the chances are also increased by being overweight or older.