just wanted to update you guys. I agreed to it and we decided we'd set a trap to get her brother involved. We started making out and playing on the couch knowing that he would arrive home soon, hoping that he'd get horny and get involved. It sorted of worked as he came over and started playing with my leg and trying to kiss me but it all got a little bit fucking weird and I had to leave. I don't know what happened with my girlfriend and him afterwards but I don't really want to know.
I broke up with her after that and haven't seen her since. Fucking weird family. Probably should have realised when she showed me a nude photo of her uncle one day.