It actually isn’t a myth. Many animals are hermaphrodites, meaning they have both female and male genitalia. And it also happens to humans, as a mutation.
Aside from having an ambiguous-looking external genitalia, true hermaphroditism in humans differs from pseudohermaphroditism in that the person’s karyotype has both XX and XY chromosome pairs (47XXY, 46XX/46XY, 46XX/47XXY or 45X/XY mosaic) and having both testicular and ovarian tissue. One possible pathophysiologic explanation of this rare phenomenon is a parthenogenetic division of a haploid ovum into two haploid ova. Upon fertilization of the two ova by two sperm cells (one carrying an X and the other carrying a Ychromosome), the two fertilized ova are then fused together resulting in a person having dual genitalial, gonadal (ovotestes) and genetic sex. X
Tl;dr: Human hermaphrodites have both XX and XY chromosome pairs and both testicular and ovarian tissue.