AFAIK if the relationship started BEFORE one of them turned 17? or 18? then they are protected. So a 16 y/o dating a 14 y/o would be protected if they are still together when they are 18 and 16. Something like that.
Before anyone asks there was a scene in the Mark Wahlberg transformer movie where a kid had the law lamentated in a card in his wallet so he could pull it out and explain to Mark that he is legally allowed to fuck his underage daughter… so I had to look up wtf that was about.