Twins of different genders are universally accepted as a sound basis for a clinical determination that boy and girl twins are not identical However, in extremely rare cases, boy and girl twins can stem from the same fertilized egg Twins, who stem from the same fertilized egg, are called monozygotic twinsIt all depends on which type of sperm The terms identical and fraternal don't describe what the twins look like, but actually how they form Identical ( monozygotic) twins are always of the same sex because they form from a single zygote (fertilized egg) that contains either male (XY) or female (XX) sex chromosomes Fraternal twins can be either two girls, two boys, or one of each
5 726 Boy Girl Twins Stock Photos Pictures Royalty Free Images Istock
