I don't know what the laws are in North Carolina but I agree with you that he is WAYYYYYY too old for her. It doesn't sound like a healthy relationship to me at all. Hopefully she can see this soon (which she probably will not at her age) but also at her age you have to allow her to make her own mistakes and hopefully things work out. You are the sister and not the parent so unfortunately I'm not sure there is much you can do.....