How do I ask such a question?

I’ve been wanting to ask my father this for a long time now but I don’t know if I should or how to in the first place. I have this memory I think of my father beating my oldest brother in the kitchen and my brother bleeding and crying. My oldest brother isn’t blood related with my father at all. My dad just kinda took him in because he was my moms son. I remember thinking for the longest time that it was just a horrible dream I had but I remember when I was 18 at my moms apartment I asked my oldest brother and my mom if it was real. They didn’t reply for a good 20 seconds or so and just started getting teary eyes. My brother then tells me he’s forgiven my father. I haven’t forgiven my father however because he’s never apologized to me or even explained to me what happened those nights. I don’t think he thinks I remember because he probably assumes I was too young. I know it didn’t happen to me (as badly) but it still traumatized me because that’s my brother and he treated him like a punching bag. And what’s worse is my second oldest brother saw the whole thing too every other night but tries to act macho about it like it never bothered him. My second oldest brother has even questioned me for feeling so bad about that. Makes me feel like my second oldest brother doesn’t give a shit about him. They’ve both told me it was real so many times after that but I want to hear my dad confess the truth. I love my father but I also hate him so much at the same time. How should I bring this up to him? Should I even bring it up to him? Should I just bring it up to him when he’s on his death bed someday? I don’t want to believe this even after my mom and my brother have told me but I wanna hear my dads side of the story. I want to make sure it wasn’t just a nightmare.