These twins can be the same or different sexes and are no more alike than any brother or sister, despite being born together. In this case of semi-identical, or sesquizygotic, twins, the egg is ...

semi-identical or sesquizygotic twins. Identical twins - when a single ovum (egg) is fertilized by a single sperm, then splits into two, producing two identical boys or two identical girls.

Even fewer cases of semi-identical (sesquizygotic) twins have been reported in medical literature. In these cases, a single egg is fertilized by two sperm. The egg then divides and develops into ...