My dad 49 male (stepdad since I was a year old) starting fucking my best friend 23 female. A little background info. my family and I moved out of state when I graduated high school. In the new state I found mutual friends from my best friend growing up and we all started to get really close. Me and my bf got an apartment w one of them and her bf. And then covid hit. So I started working for my dad’s business and also got Britney a job working with us. It was all going fine until my dad asked Britney to be the supervisor and not me ? We have never had the same last name and look nothing a like. His excuse was he didn’t want work and the job accounts to think he was just picking family. Even though his whole damn family is working for him. But he started taking her out of town for “work”. me and my mom had our suspicions. And then I would ask to hang out with Britney and she would make excuses to why she couldn’t. In the back of my head I always knew there was something going on. For Fourth of July my mom was in a different state bc my great gma was dying so she was up there helping her family. Me and Britney decided to go to my dad’s sisters house. (My boyfriend is not a fan of his family and I am not either bc his father molested me for years and went through all the court and shit being really young was tough. But all of his family still lets that man around all their kids and new babies.) my dad literally tried to give me alcohol poisoning. I don’t remember anything from that night but when we got back to stay at my moms and dads house. My boyfriend was up and trying to check on me bc I guess I was just bawling and drunk. My dad would not let him go into the room to sleep w me ? We live together and moved states so that was weird. But anyways my dad and Brit were up all night talking outside on the back porch. In the living room there is a window that looks right out there so my bf was just sitting on the couch watching them all night bc anytime my bf would get up to check on me my dad would yell at him to go to bed and not worry bc he got me covered. But clearly he’s too busy trying to fuck my friend he was not checking up on me. I woke up choking on my puke. I honestly thought he was trying to kill me. I don’t drink and don’t even remember drinking that much that night. My mom was beyond pissed when she found out. More things were just pointing to the fact that they were having an affair. Even people at work were starting to catch on. I’ve asked him multiple times if he and Brit had soemthing going on and he told me no everytime. But My dad was catching on the fact that I was pushing myself away from them and we met up at a Starbucks where he cried. Literally cried bc he didn’t want to lose me as a daughter I’ve never seen him cry so I knew it was just straight bullshit he was feeding me. He is an abusive drunk when I was little I would have to pull him off of beating my mom or holding my mom down. He’s very narcissistic and good at making you think you need him for anything. A couple months go by and my mom had a credit card statement for a hotel in state and she asked me to check Brit’s location on find my friends. Brit and my dad’s location were at the hotel my mom got a charge for. They were at the hotel room up the street. They just didn’t care to go on a work trip to get away w it this time. Flash forward to today they are still together. My dad took my sister and Brit and bought a house in a tiny ass town of 666. Very fitting. But I just want to know am I the asshole for not wanting a relationship w my sister ? I just can’t fathom the fact that my sister is living w her dad and his gf who is only 3 years older than her. And my sister won’t talk to me nor my mom and think we are in the wrong for being betrayed by him?? She is very unstable mentally. But she lives on tik tok and her phone but I never receive a message back so I just stopped reaching out to her. She seems to be doing a little better mentally but I just don’t want to push her to the point of depression. But do I even tell her how I feel ? She clearly has never asked me but I also didn’t want to bash her dad infront of her so I’ve never said anything negative infront of her about him. Sorry if this is too long or too much info this is my first post.