Similar circumstances for my parents although they never blamed me.
Am so sorry you had to deal with all of that.
Far too many people have knowledge of things they shouldn't. I know my next half brother up from me was 'forced' on her so that she didn't leave. She left anyway. And my God, even if she never said the words, he knew she didn't want him. I also know that the only reason I'm around is that she didn't notice she was pregnant for months. Which makes sense if you take into account that a) I'm ten years younger and b) she kept me off the radar/out of all non compulsory school provision/away from other children/sent to a different primary in the hope that there weren't any teachers who knew the family background (which backfired as one of my teachers actually taught him at the previous school, so knew all about his being one of the first children on the At Risk register when the concept was first introduced).
I also know that I 'nearly killed her' by jumping on her stomach aged 4 when she had a grumbling appendix. Apparently, I ruptured it because I unreasonably wanted things like physical contact and
ewww weird child cuddles, which 'we don't do because the Queen doesn't with her children'). Bollocks. But that's the narrative.
ETA: at least it's just the things I heard directly - had she been a SM user, we'd all have been able to find out her opinions. Which wouldn't have been pleasant - except for one of the kids, who can still do no wrong and feels the same way about her. Although it would have been enlightening for him to see her wishing the eldest son dead as she never liked him either - especially when he died and she became this pitiful 'oh, he was so good to me doing everything, I don't know how I'll cope without him
and his money'. And what the conversation about his Death in Service benefits actually entailed (PUT ME DOWN. ME. NOBODY ELSE. And him saying he wasn't going to do that. She got the Death in Service benefits, so is now absolutely minted.)
SB is going to know everything she says about how he ruined her life, body, etc, etc. And the truth of the stories about how lovely everything is.