The blues can be monozygotic (identical), which means they develop from one egg, which splits and two embryos are formed. They can also be dizygotic (fraternal), which means that each of the two twins develops from a separate ovum, which is fertilized by its own sperm cell. The explanation for the formation of dizygotic twins lies in the fact of the mother's hyperovulation, which is the release of more than one egg during ovulation. This fact again depends on the mother's genetics.
