The Concept of You and Me

     Our David is four now and of course talking more in sentences and we are trying to explain the concept of you and me. Sounds simple, doesn't it? Try it, it's not as easy as it sounds, in fact it's down right confusing. We have him point at himself and say me, but to him, me is us, and you we  point to ourselves, but he thinks he is you to us. We think we almost have it but our little conversations with him sometimes prove otherwise. Any suggestions?