AITA for wanting a relationship with my adopted sister without my adopted brother in the picture?

TW/CW: molestation . . . . . . … So I come from a family that decided to adopt two children that were older than me from Ukraine. I was 13 and they were 15 & 17 when they got adopted. I have sooooo much to speak on on this, but that is for another time. Important details to include would be that they hazed the crap out of me on the Native American reservation we were regulars at on about how siblings that are adopted are still siblings and NOT TO BE VIEWED AS SEXUAL. This was drilled in to me to the point of being obnoxious 2 years before they were adopted. Another good detail to include is that in spite of being a flirtatious person at my current age, 30, I was a suuuuper late bloomer with sex!!! I didn’t date or do anything with anyone in high school and did not consentually have sex for the first time until I was 18. So here we go: When I was 21, we all took a trip to meet my mother and extended family for a family reunion in Chicago. During this time, my adopted brother molested me in our hotel room, and I literally ran away, met a nice lesbian couple in a pool hall, and stayed with them in THEIR hotel room at another hotel for the rest of the trip. When my mother got there, I told her what had happened and she told me that if I called the cops or told ANYONE, she would make me homeless. She helped me with my rent while I was going to school on my own money since all of my designated college funds went to sending my adopted siblings to college. I didn’t let this last part bother me because most people don’t have mothers who could afford to send 2 kids to school in the first place. I used this knowledge to force myself to check my privilege extremely regularly. But being told I’d be homeless scared the crap out of me. So I stayed silent for years. My mother heard my brothers side out fully and then refused to hear mine for 6 years. (In spite of the fact that the VERY FIRST phrase we learned in Russian was “(insert brother’s name), ne trogay” which translates to “(insert brother’s name), don’t touch!!”) She said that he said I was asking for it so she believed him. I was asleep and woke up to him molesting me and immediately jumped up and locked myself in the bathroom. That family reunion, I hid in the basement the entire time to get away from my adopted brother. My family said I was acting weird, but he got to roam around on the top two floors and outside, and dance and sing with my family, and thankfully left me alone to hide in a corner in the basement crying. Why is it coming up now that I’ve just turned 30? Welllllll, I proposed to the man of my dreams almost 2 years ago and we’re getting married in April. Boundaries first started occurring about a year ago when my counselor convinced me that I didn’t have to have my molester at my wedding. When I first told my mother I didn’t want him there, she FREAKED OUT. She was incredibly angry and told me that it was my fault he did it and that if I don’t have him there, then I’m the one ruining the “happy family”. 🙄🙄🙄 As though 3 divorces between multiple sets of parents and getting beat up by dudes that weren’t my dad but pretending to be didn’t do that already. She has since 180-ed on her opinion since she went to the counselor that she stole from me and tried to tell her I was being dramatic for what I wanted… well the counselor then reminded her of the US law and somehow, now my mom is suuuuuuuper supportive. Wish it had been sooner, but I’m proud of her regardless and I applaud her growth!!!! 👏👏 The problem now is my adopted sister. She keeps telling me that since he’s said he’s sorry, I should just forgive him because it makes family events difficult. Mind you, I’ve been the one seeing all of my family members separately and avoiding family events for years. He’s stolen my adopted family, and he can keep them for all I care. But I think it’s fair for me to attend family events with my mother’s family and he can be the one to schedule separately with her. My mom and I have agreed to start trying this. That’s fine. What I don’t like is that my sister says I have to be around him for her holiday birthday events, or else not celebrate them at all. She says what he did was messed up, but he said he’s sorry so I should just move on in the sense of forgiving him, rather than cutting him out. What I truly want is to have a relationship with my sister outside of him…but if she cannot understand or respect why I don’t want to see him, then I don’t know if having a relationship with her is conducive to my health. I’m only just finally starting to gain basic self worth after setting these boundaries. I can see it and it’s huge!! I’m also very scared because I was not allowed to have these sorts of boundaries growing up. Am I the asshole for wanting a relationship with my adopted sister without my adopted brother being in the picture? Am I the asshole for not wanting him at my wedding or in my life at all?