I wish I had something profound to say...but I don't. This is just messed up and my heart goes out to you.
Our situations are completely different but I'm going to share something that I hope has some relevance and most of this you already know.
When I confronted my half brother he told me that my middle brother (10) had 'started' it with him (16). Because he was being abused by another boy (I know this is true). This really rattled me for a few weeks. I had always felt that my middle brother was also abused by my half brother and then abused me (6) because of what he learned. I have always been closer to the middle brother and did not blame him for what he did. You could say he was my hero.
This new information completely went against what I 'knew' to be true about my middle brother. We were both victims of our half brother. The only way I could confirm this story was to talk to my middle brother about it. His life is going pretty well and I did not want to awaken 'this' in him. Because 'this' is hell. So I left it alone.
I decided to go with my original feelings about my middle brother....He did care form me and protect me at times - but was confused and did stuff to me that wasn't his fault.
This may not be totally true but it is what I choose to believe...for now.
More than meets the eye!