Okay, first of all, it's not illegal. Not at the state we know its at: a teenage romance. There is nothing that would indicate that they've done anything to illegalize their relationship, and if I know Joel well enough, he's not the type to take advantage of a situation like that. Actually, from what I've heard he's taken a celibacy vow. Not sure how true that is, but at this point, I've seen nothing to make me believe otherwise.
Ugh. I had to defend Joel at a GC forum too.

But, I think (now that I'm over my little pretend-jealous [of both] phase) they really do look cute together. From the pictures I've seen, they both look happy, Hilary especially. And if that's the case, then all the power to them.
Love knows no boundaries. Age is merely an obstacle.
