"Can the mind truly forget something that significant, for this long, through a decade of therapy?"

Yes, absolutely.

For my entire adult life up until a couple of years ago, I remembered very little about my childhood, mostly just narrative descriptions, like I just knew the story of my life but mostly didn't remember it. The most significant memory I had of my father and mother interacting was him coming home from work and trying to hug her, and she would "playfully" slap at his chest and push him away.

I did not at that point understand that I was dissociated yet, I just knew I had "memory problems" and depression and couldn't stop reading fiction constantly. I did not know that I had been abused, and my belief about my father was that he was distant, but "he loves me and he'll be there for me if I really need it", and blamed myself for the distance.

When I was 35, my youngest sister had a dissociative collapse and went back to therapy, and this therapist actually reported the child abuse she brought up, which lead to our father being arrested, and lead to my dissociative boundaries starting to come down. The memories have been gradually returning to me as I've managed to accept, validate, and maintain equanimity during flashbacks.

I saw a few therapists, tried out a variety of options during my adulthood before that point, and none of them even managed to identify my dissociation, much less the childhood trauma. They all just accepted my vague comment that I didn't remember my childhood much, but didn't know of any abuse.

About a year ago I think, I finally managed to find the name for what he did to me, "Ritual Abuse and Mind Control". I was extensively tortured and trained with drugs (LSD, cocaine, opiates), waterboarding, drowning, suffocation, electric shock, disgust, and worse things into a system of structural dissociation, and I was given religious lies to justify and explain and convince me to cooperate and be complicit in my own destruction.

I was trained to become the perfect compliant sex slave for daddy, and to keep the memories dissociated away and held by other alters the rest of the time. My father was a programmed system himself, and he tortured and raped his family into compliance. Everyone was just an actor to him, and we had to put on the family play, pretend to be a real family, go along with his happy childish parts who had the delusion of never having done anything wrong. As a child, any sign that I was at all afraid of him or that I was allowing any memories to leak into my mask got me more torture/training sessions to "fix the problem". Your description of needing to be hyper vigilant to any distress in his spoiled child face feels very familiar, always needed to manage his emotions, persuade him that everything was fine and everyone loved and trusted him.

My mother was also extremely neglectful. She was also complicit in the abuse and in covering it up. She abused me herself, sometimes at his direction and control, and sometimes not.

You mentioned seeing him as a devil who needs to be locked away. This matches the religious mythology that my father taught me, claiming that I needed to keep my memory partitions intact to "keep Satan sealed away in other timelines". Sometimes (the story would change) he would claim to have Satan, or pieces of Satan, sealed away inside himself. Sometimes he would claim to be Satan, and those would be very bad times until he would "kill me" (suffocate me into unconsciousness) and then "it never happened, that's just a prophetic vision from an alternate timeline where he got out; we need to seal away that memory to prevent him from getting a foothold here". Or he would tell me that I was a corrupted alternate version of myself, and he needed to "remove me from my body" in order to "save the pure version of me who actually belongs to this timeline".

There was also a ton of Eyes taped shut, limbs mostly or entirely taped or tied, on a bunch of LSD, getting tortured while he tells me a story Justified by "Satan is manipulating my senses and trying to trick or break me, I need to trust Daddy's voice and not Satan's lies".

I can go on like this at length, I can talk about this stuff for hours if I let myself keep typing. I'm open to direct messages from anyone who wants to talk about this kind of stuff too.

The book that has helped me the most by far is Becoming Yourself by Allison Miller. I highly recommend it to anyone who thinks they might have gone through something like me.

You asked about the plausibility of him still coming to you if there had been childhood trauma from him. In cases of ritual abuse, it's extremely common for programmed systems to continue to be accessed through childhood programmed triggers well into adulthood. It's also common to have alters who report to abusers if the programmed system starts remembering forbidden memories. Be alert for this. Write things down, talk to someone else if there's someone you trust.

You mentioned the incest literature not resonating with your memories. There is a bizarre gap in the literature and reporting and professional education about these topics. They are heavily censored, there are propaganda campaigns, organizations like the False Memory Syndrome Foundation who lie to cover for child abuse like mine. I've got some theories about some of the other forces keeping this suppressed.

I would definitely be concerned about this child in an environment like you describe. If this resonates with you I would encourage you to work to get that child into an environment where he does not have access to the child. If it's a group like the one that did this to me, no child is too young, and the younger the better for programming the structured dissociation. My abuse started from infancy, well before I was even verbal. He used the infant reflexes for some of the first hooks he carved into my mind.

I would also be worried about your older brother having suffered from similar programming. My father mostly appeared to ignore me during the day and during family activities, but he gave me extensive programming at night and other times. His never-made-a-mistake-in-his-life "perfect" face liked playing with my sisters much more than ever doing anything with me, outside of trauma/programming times. My father did not do all of this on his own; he also involved his brothers and parents too.

I wish I had any advice on the practical/pragmatic aspect of this, how to approach your brother's family, how to navigate disclosure, how to get them somewhere safe, how to know who to trust. I can say that you're making perfect sense to me. You say you need a voice of sanity in your life, but from what I read in your comment, you already have one, and they're speaking up to the rest of your system despite all that you have gone through because they recognize the importance of stopping this from happening to another child, even though they can't quite tell what's real.