They also have to be under a specific age of consent, which changes from state to state. I believe it ranges from 14-16 with 16 being the norm. The thing is, while it isn't socially acceptable to be sexually attracted to a 14 y/o when you're 25+(and lets be honest, that's fucking young), a 14 y/o is still sexually mature from a physical standpoint. That is not CP, creepy yes, but not CP.
well maybe not physically, but legally it still remains- and as a belief I think that it is not the physical maturity alone that allows the relationship to be adult but the mental maturity which doesn't directly correlate with physical/sexual, for example as a 13 yr old I would have been totally capable of having sex with a legal adult physically, however it is important that society recognises that the reason that would be wrong is not only due to the lack of complete sexual/physical maturity but the ability to make decisions which are of that degree of importance