Twist his arm Viv by all means.
He might find comfort from reading even if he wouldn't want to post. He would also have the option of asking somebody directly (via the name under the profile picture) if something appeared on screen that he feels he'd like information on but it's too personal to write down.
He could have private conversations, one to one, with a member who he can see is going through the same as him.
Worth pointing out anyway.
Has he ever looked at the site or does he just know about it from what you tell him. Perhaps if you show him the page he'd be more comfortable viewing for a while before joining.
Anyway, glad you've found us helpful !!