I have to add that my brother in law (who unfortunately lives with us right now, long story) has a similar attitude. Sometimes I wonder if he feels like I've stolen his big brother away from him. What I've vowed to do is that no matter how annoying his behavior may become (he has told my husband that I hate him and that's why he's acting this way), I'm always going to be nice to him, treat him like family and eventually I WILL wear him down. I do agree with Jadzea that maybe he's afraid he won't see his brother as much anymore and really wanted some bonding time. Either way I would take the high road at all costs. Otherwise you might regret something later. The whole situation isn't cool though. I send hugs your way