23 f I sucked my older sister's boyfriend's cock behind both her and my boyfriend's back

My sister and I are really close so the only way I can justify this is that I was insanely drunk. It was late at night and I had been getting really drunk at a local bar by myself and got into a bad situation. I'm not gonna go all into detail on that but I called my sister to come pick me up. We drive back over to their place and they let me spend the night since I am extremely fucked up. Anyway we all hangout for a little bit but since it was so late they went to bed and I was just watching tv on the couch. A couple hours later her boyfriend comes out to get some water and I ask him if he wants to keep me company for a bit because i'm bored. He agrees and we sit and talk for a little. He ends up ranting about how my sister nags at him and how they haven't fucked in weeks. I start to feel really bad for him and tell him I can help relive his stress. I started rubbing his cock in his jeans until it got hard and he told me he shouldn't do this but since I'm so much hotter than my sister he's going to but I can't tell anyone. I take his cock out of his pants and start kissing the tip and spitting all over it. His dick was fucking huge I started sucking it and could barely get it down my throat. He got really rough with me and slapped me before pulling my hair up and brutally forcing his dick down my throat. There was so much spit and I gagged so much. He shoved my head down for a long time and came deep down my throat and thanked me for sucking him off and then he went back to bed with my sister.