Whatever you do, don't shun him, no matter what happens. If your homophobic, at least try. It was nothing you did in your parenting, its just him. Just be supportive of him. If he is gay, he will need the support, because he is likely to loose a lot of friends, looked at weird, made fun of, possible beat up, if this gets out. Hopefully it does not. But just let him be himself, and don't let him isolate. Try to get him to tell you, don't confront him about it.