How do we get identical & non-identical twins?
Identical twins are formed when the fertilized egg splits,thus developing into two seperate fetuses.This would mean that identical twins are always the same sex.Fraternal twins occur when seperate eggs are fertilized at different times.It is possible that a woman have sex with two different men and be impregnated by both men.This means that a woman could carry a set of twins that had different fathers.Strange,I know.But true.Then there is a rare instance that two twins can merge or one absorbs the other in the early embryonic stages and become one but have two different DNA strains.They are called Chimeras.
