Identical twins almost always have the same sex, but can have different genders as they grow. In very rare cases, identical twins can be born with different sexes due to genetic mutations. Fraternal ...

Fraternal or dizygotic twins develop from two different eggs fertilized by separate sperm; they generally share about 50 percent of their genes. Therefore, fraternal twins are essentially like typical ...

When I was a child one of my favorite books was about a pair of identical twins who decided to switch clothes. They looked so much alike that their parents had had to dress one in blue and the other ...

NEW YORK (Reuters Health) - The prevalence of early menopause, also known as premature ovarian failure, among identical and fraternal twins is triple that of women in the general population, according ...