Question

How are twins born ?

Answer 1

Sometimes a fertilized ovum splits itself into two individuals and starts to grow into uterus.Thus monozygotic twins are born this way. Sometimes in rare conditions two ovas are released by the ovary and they are fertilized by two sperms.Thus dizygotic twins are born this way.

Answer 2

The two eggs, or ova, form two zygotes, hence the terms dizygotic and biovular. Fraternal twins are, essentially, two ordinary siblings who happen to be born at the same time, since they arise from two separate eggs fertilized by two separate sperm, just like ordinary siblings.