I think everybody gets their heart broken a few times before they finally connect with someone? I would start to disengage with your "friend" and hopefully he'll try to engage more with the girl to compensate? Just use "natural" excuses (if you need them) like you and bf are going somewhere/doing something but generally make yourself less available. I think it is very nice of you to care about him and his crush on you but you can't really live his life/"help" him with other girls or worry about his love life without jeoparding your own. He's got to learn to deal with any crushes he gets on "married"/unavailable women :-) as well as getting his heart broken and if he gets any sense of "bait and switch" on your part that might jeopardize his and your bf's friendship.