I would also point out the human trafficking by pimping out your own child. Really need some sort of extra charge for that one, something about abusing a position of power.
There actually is in a lot of states. There is a specific charge for, "sexual abuse on a child from a position of trust", that is specifically used for parental guardians. The charge is treated as a higher class than just sexual abuse on a child by itself, and I think the minimum is around 10 years for it. It should probably be higher considering people go to prison longer for drug charges, but at least its something.
I learned this from watching too many true crime documentaries.
I read this article about an underage marriage, and while it explains how they get to that point in a more specific way, these are still men who rape children incapable of consent. No matter how you slice it, it's rape.