Either the instructor at Hero or WW in one of his streams (I can't remember) said that certain monsters are capable of reproduction, and because of that superhumans can reproduce with them, so it's more about the monster than the superhuman in this case. Though that might mean certain superhumans might also be able to reproduce. Nothing yet suggests that MC is one of them, but I suppose its technically possible?
Regardless, I'm pretty sure MC could transform himself into a form capable of reproduction once he gains enough skill in transforming, but who knows.