There are identical twins and fraternal twins. To form identical twins, one fertilized egg splits and develops into two babies. To form fraternal twins, two eggs are fertilized by two sperms and develops into two different babies
There are conjoined twins which are formed, a single egg develops into 1 baby. Sometimes a single egg divides in half 1 to 2 weeks after it's fertilized. This creates a set of identical twins. The exact cause of conjoined twinning is not known.
There are non identical twins.Non-identical twins form from two completely separate eggs which are fertilised by two completely separate sperm. These fraternal twins are no more alike than any other siblings in a family with the same biological mother and father. Because identical twins share the same genes, they are always the same gender.
