Fraternal twins are actually the most common type of twinning. While identical twins happen for no apparent reason, fraternal twins come about due to a number of factors, like hyper-ovulation, age of the mother, fertility treatments, and hereditary influences. read more
Fraternal twins can be boy/boy, boy/girl, or girl/girl. Identical twins are the result of one fertilized egg splitting. The split usually happens around days 4 or 5, after the placenta and sac have started forming. Which means the two babies end up in the same sac, sharing the same placenta. Identical twins are always boy/boy or girl/girl. read more