What is a fraternal twin?

For fraternal or dizygotic twins, they develop from two different eggs fertilized by separate sperm; they generally share about half of their genes. Therefore, fraternal twins are essentially like typical brothers and sisters. For more on identicals and fraternals, visit Identical Twins and Fraternal Twins.

What is a nonidentical twin?

Nonidentical twins are generally known as fraternal twins. The scientific term for fraternal twins — “dizygotic” — refers to two fertilized eggs. Dizygotic twins happen when the birthing parent’s body releases two eggs at the same time. A different sperm will fertilize each egg.

Are twins hereditary?

Fraternal twins, also known dizygotic (DZ) or nonidentical twins, are twins that result from two separate eggs released from the ovary and fertilized by two different sperm cells within the same menstrual cycle. The two fertilized eggs implant in the uterus and develop during one pregnancy.

Are all twins identical?

Not all twins are identical, of course. More often than not, twins are born with unique physical characteristics. Nonidentical twins are generally known as fraternal twins. The scientific term for fraternal twins — “dizygotic” — refers to two fertilized eggs.