Have to agree with Steve2.
I was a gay JW in my mid twenties who had to put up with people asking if, or telling me, I was gay. It wasn't at all helpful. I came out when I was ready/couldn't bare being closeted anymore. Being supportive when someone comes out rather than trying to prise them out is how you help. If he knows he's gay, the chances are he'll know the resources available, there's even online support for gay JWs which, as much as I personally think it's a nonsense, does appear to be genuine. http://www.witnesses.plus.com/