Without knowing more about those involved I'd say that the girl must have some issues if she's prepared to settle for a 16 year old and the guy must be one of those lucky ******** I keep hearing about. You know, the type that end up having sex with their teachers and their best friends' mums.
I have to say I know a guy, who's in his 30s right now, he's been with his (much older) girlfriend since he was 16.
He cheats on her constantly.