I often hear about people who black out or blank out past sexual abuse that occurred when they were younger. I must admit that I really didn't believe all of them, but I personally know of incidents from the past that these same people claim they don't remember.

I remember catching a younger brother
fucking one of our sisters, she was 4 years younger than he was and I screamed at him and told him to go down stairs. I told her to lay still and I rubbed her bare bottom for a minute. I was extremely hard and was going to fuck her also, but after caressing her bottom and super wet pussy, I decided not to, because she was after all, my sister. I told her to get dressed and to not do this again. I went downstairs and gave my brother a thorough verbal lashing and demanded that he never touch our sister again. I don't know if that was their first time or even if it was their last time.
That was over 40 years ago. Recently I asked him about it and he vigorously denied it ever happened.
I asked him about a cousin of ours and he denied ever fucking her also.
I reminded him that we, me and him had fucked her at the same time at her house when we were teenagers. He swears it didn't happen.
Just this past 4th of July, this same cousin brought up the fact that she had loved all her family and sheepishly mentioned to me that she had fucked over 17 male cousins, including me and my brother. I told her that he doesn't remember that and she said, well we are all getting older and memories fade.
I say this,because on numerous occasions, people claim they don't remember the bad things that happened to them. I was abused at 8 years old by a 30/40 year old neighbor. I willingly let him fuck me in the ass.
No one knew then and no one knows now, but it hasn't been blocked from my memory.