Most of the tissue in reproductive system is the same between male and female, it just develops in a different way depending on hormones, so a real-life futanari with fully functional male and female genitalia would require duplicates of everything and some system that causes half of the copies to develop along the male pathway and the other half along the female pathway. And some kind of system to trigger purely female secondary sex characteristics despite having testes pumping out testosterone. Ain't gonna happen unless some mad scientist with technology several decades beyond what we have now experiments on people to make it happen.
Trans and intersex people, on the other hand, do exist and deserve to be treated like people, not fetishes.
