>>4 Then I don't see the relationship part of this being an issue. Perhaps you should look at it as helping a person in need, instead of the relationship being any part of this. In fact, ignore that entirely.
Rather, if you TRULY think they might do something to themselves, go straight to his parents, but in private. Tell them what is going on, and suggest something along the lines of a suicide watch to make sure they don't try anything so absurdly stupid.
I was on one once, and they're surprisingly effective if nobody lets their guard down. That said, they let their guard down, and they didn't find me until four hours later when they got a phonecall from the police... Oh, look, I'm rambling. Sorry.
Just go straight to their parents, and start taking special care -without being obvious- of the situation.