I had drunk anal sex with my brothers wife after last years x mas get together. It was at their house. My brother got food poisoning from his work x mas party and stayed in thier room all night. After everyone left her and I continued drinking. Flirting led to kissing which lead to me fucking her in the bathroom. We were having regular sex when she says “stick it in my ass” I pulled out she got a tiny container of lube from the sink drawer and used her hands to spread it all over my dick. She was my first anal so I was nervous. It popped right in and instantly I knew I liked anal. Her asshole was way tighter than her pussy. I came in her ass and went to the guest room to pass out. In the morning it was like nothing happened she made breakfast and acted normal. Now everytime I see her all I can see me fucking her ass. It’s made this year’s gatherings difficult for me. On top of that I often get a reflexive boner when I look at her ass( which I try not to do). And I feel deep guilt when I look at my brother. I don’t regret what we did because it was amazing but I know I betrayed my brother. Just have to hope this one goes to the grave with me.