OK, this is a very big controversial theoretical question that has been going around my school for a long time.
IF a pair of conjoined female twins, with two heads but share the same torso, are having sex with a man, but one of the twins does not want to have sex, is it considered rape?
Another similar question would arise if one of the twins was masturbating when the other one did not want to. would one twin be raping the other?