I'm not sure about the purity ring because I don't even know what the hell it is, but I'd be more concerned with him turning out to be one of those men who let's his woman walk all over him. For the sake of all real men, I think you should intervene.
Your cousin may have a social advantage being raised by women: not calling everything wierd "gay," for example... In any case, I'd prefer they get him a crate of condoms to go with his patriarchal fantasy ring; but otherwise I think it's fine.
