How do you have identical female twins?
Luck. There is no way of having identical twins, let alone
choosing the sex.
There are two primary types of twins, Identical and
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. Fertility drugs also make this more
likely to happen.