Growing?

My first experience with sexual abuse started with a step sibling who was a year younger than me and we are the same sex and gender, but of different orientations, they are gay, and I am bi, but in a heterosexual marriage for the last 15 years. I don't remember many details, and the ones that I do, I'm still not comfortable sharing with ANYONE, not even my spouse or best friend. Those two are also the only people I've ever confided in about it. I'm sure my step sibling has possibly shared with someone. We are both 80's babies to give some context as to how long I've held onto this. The only reason I feel I can even share here is the anonymity, my spouse is the only one whoever sees my computer as well, so I feel a lot safer. I struggle to find blame in either of us. I want to, but because my memories are so fuzzy with it, and I don't know how, or why it started, or how long it went on for, or who initiated. Not even sure it would matter, but I think it may have stunted me more than it did them. They have been out for quite a long time, whereas with me, I just recently came out as bi. Throughout the course of my relationship with my spouse, I've had hang ups about feeling attraction to the same sex. They would always tell me, that it likely stems from the abuse. I agreed with them, but I have never been in a place where I wanted to visit the subject again, or even look into healing from it, because that would mean I would have to share. I never wanted anyone knowing because I felt so much shame, I felt shame as it happened I remember, or at least acted like it. I do really wonder who initiated because I always thought it was my sibling, but it could have just as easily been me. I don't know how either of us would have known to do such a thing at that young age (the last time I spent a 6 week summer was when I was 11, I got diagnosed with Type 1 diabetes in the fall of that year, and my mother got really protective of my care). There's one inkling I've had that I've not shared before, but I remember our 13 year old babysitter letting us watch porn, I just don't remember what age we were, but I believe the babysitters name was Amy. My Dad and stepmom did find out about that, and I think Amy got let go, but I'm not sure that this happened before the abuse started, I think it may have happened prior. At some point soon, I plan to find a therapist that can help me uncover some of the memories, but going through this here, has opened some doors on memories of other assaults from my adulthood. I'll add those stories later, because this has been a lot.