My brother and our close mutual friend have been staying in my guest house since me and my wife bought our place. They have the means to get living spaces of their own, but we all enjoy this arrangements. In fact, I was specifically searching for a home with a guest house space. We split the utilities, but I don't charge them rent.
There's an open door policy when it comes to me coming and going. I'll usually go hang out with them after dinner, and sometimes if I can't sleep I'll go hang out. They're welcome to come hang out at the main house anytime they see my car in the driveway so they know I'm there. Occasionally my wife will join us for these hang outs but it isn't often. She and my friend/my brother seem to have conflicting personalities.
An incident occurred two weeks when my friend came home and found my wife standing in the living room of the guest house on her phone. This was obviously strange and a little off putting, but he just greeted her and went to his room. She left a little while later. He brought this up to me, but asked me not to say anything to her. He figured there was a logical explanation and didn't want to cause issues.
The same thing happened to my brother. He came home a few days after the first instance, and she was in the living room on her way out. He was confused and asked her what she was doing, but she just brushed things off. I wasn't told about this when it happened. The final straw came just a few days ago when my best friend came home and found my wife in his actual room. He was obviously caught off guard and kind of raised his voice asking her to leave.
After I was updated on these final two instances, I spoke to my friend and brother about what they wanted to do. We finally decided to get the locks changed on the guest house doors. They were creeped out and felt unsafe with their privacy being invaded. When my wife discovered I had done this, she was livid. I tried to ask her why she kept going into the house, but she wouldn't tell me. She just kept reiterating that it was part of her home and she should be allowed to go in it.
This whole thing has me confused and a little freaked out. AITA?
Edit: My brother and his friend have to knock and be invited in before entering our house. They can't just barge in, even if they know I'm there.
Edit 2: I pay 80% of the mortgage. At one point, I was paying 100% of it. My brother and his friend have offered to pay multiple times and always remind me they would like to. They also contribute to the house in other ways, like buying groceries and fixing things there and in the main house.