BIL is staying with his dd (my dn) who is 10. She is sharing with my dd age six. Before bed my dn asks for tickles which BIL does all over her tummy, arms etc in quite a slow, strokey way. I'm sure it's completely innocent but makes me feel v uncomfortable. My dd is then begging me to tickle her like that which I am not going to do, and then her cousin says its ok, she will tickle her like that - luckily they fell asleep before any more tickling occurred but it has made me feel a bit sick. They are staying and the girls sharing a double bed for the week. Want to say something to bil but he will think I'm mad and probably be offended. Probably just sees it as something innocent that his dd likes. My DH thinks I am totally unreasonable and neurotic to even worry about it. What should I do/say?