I agree. It doesn't have to be a big "sit down we need to talk" talk. Maybe just a "gosh I'd love to have a little boy who looks just like you" or " A little girl of our own would be so special" Nudge nudge hint hint. Test the waters without making it seem like a big deal. He might be thinking the same thoughts and just afraid to bring up the subject with you.
Each experience in life has formed me, become part of me, made me stronger.