Up until recently, myself, my partner and his brother were very close and got on great. He has no interest in getting a girlfriend or settling down so spends a lot of time with us. He adores my kids and they love him to bits. So a year ago, we decided to all buy a house together, this is not something he would have done alone (he's not much of a go getter) my DP did all the house hunting, negotiating, etc. The mortgage is in DP brother's name but we went halves on deposit and DP and I pay all the mortgage. When we eventually sell it, we will own just less than halves. At the time, it seemed a good investment for everyone. He was moving away and in with a friend paying cheap rent, but will end up owning more than half a 3 bed house. It turns out, it was the worst decision ever. All boundaries have been shifted. He lets himself in with his key, he rummages through the food cupboards, wanders around upstairs, even got changed in my bedroom the other day! The list goes on. If that isn't irritating enough, he has started treating the kids as if they are his own, telling them off, making decisions about what food they can eat, when they can watch telly, etc. It's a nightmare! He has admitted to me, he really misses them, hence why he is moving back! The other day, he let himself in and didn't even say hi to me, just went straight to the kids. Generally he is lovely, but at the moment I just feel so frustrated. The main reason, I find it so hard to have it out with him as I think he is pretty lonely and I don't want to upset him. I am absolutely dreading him moving back though. AIBU?