Nonidentical twins occur when a woman produces two separate eggs that are then fertilized by two different sperm cells. The resulting twins sometimes look alike, but have separate genetic identities, like children of the... More »

The mother's side of the family is responsible for non-identical twins, also called fraternal twins. There is no family history when it comes to identical twins. More »

The father does not carry the gene for non-identical twins, as releasing more than one egg at a time is a trait that runs in the maternal line. There is no evidence suggesting that identical twins run in families. Women ... More »

Fraternal twins, also known as dizygotic twins, occur when two separate eggs are fertilized by two separate sperm. This results in two babies who are not identical and who do not come from the same egg. Fraternal twins c... More »

Dizygotic twins, also known as heterologous or fraternal twins, develop when two separate eggs are fertilized at the same time within the uterus. Dizygotic twins do not have identical genetics and can be of the same sex ... More » Science Biology

Artificial embryo twinning is a method of making clones that mimics the natural process of creating identical twins, according to the Genetic Science Learning Center. It uses the same approach as natural cloning, but it ... More »

The exact cause of Siamese twins, more accurately known as conjoined twins, is not entirely known. Since the prevalence of conjoined twins is thought to be higher in southeast Asian and African populations than in Caucas... More »