If fraternal twins run on the mother’s side of the family, there is an increased chance of her also having fraternal twins. This is due to genetics passed on to the mother. Fraternal twins are two babies who develop from two different eggs and sperm. Learn about their common traits, how they differ from identical twins, and what to expect during your twin pregnancy. Identical vs fraternal twins: what are the main differences between the two types of twins? Yes, there are other subtypes of twins. But, in most cases, a woman either gives birth to a fraternal twin or an identical one. The number of identical twins born is comparatively less, while fraternal twins are more common. Because fraternal, or dizygotic, twins are 2 separate fertilized eggs, they usually develop 2 separate amniotic sacs, placentas, and supporting structures. Identical, or monozygotic, twins may or may not share the same amniotic sac, depending on how early the single fertilized egg divides into 2.
