you just walk up to him, hold your hand out and ask for your key.....then you change your locks.......when he protests, explain what he did and let it go at that. you're the adult and you don't have to explain, ad nauseaum, why he isn't allowed in your home when you aren't there........

how's that for a direct answer? my daughters are in their 30s and neither one of them have a key to my house. neither does my SO or my good friend, Robert.......