Having Twins

Although identical twins are random events, fraternal twins pop up in families again and again. A mother doing double diaper duty carries a gene that makes her release multiple eggs during ovulation, called hyperovulation. Although a man who carries the gene will probably not father twins, passing the family trait to his daughter could make him a grandfather of twins. This is why twins sometimes appear to skip generations, even though there's no evidence that twins are more likely to occur every other generation.