Dont nark on him that is stupid. Go join him or get over yourself. He will eventually get out of the phase and move on with his life so mess up things for him. If you feel it's a problem for him then go talk to him yourself.
Yes you should have a word with his parents I think then let them take it from there. It might be a while before they notice anything. If he entrusted you with the situation I trust you already gave him some good advice.