This is something I don't think I will ever forgive myself for. I am a male in my twenties now and there isn't a day where I don't think about and regret what I did. When we were young we spent a lot of time alone in the house and me being a 12-13yo I didn't exactly have the purest thoughts. He was a lot younger he was around 6 or 7. anyways,I started showing him my erections and eventually we experimented and performed sexual acts such as oral sex. This happened several times until finally I came to my senses and realized I was doing something terrible. I have regretted it ever since and fear what I may have caused him in the long run. Today we get along fine like normal brothers and I love him and support him but its just hard to deal with and I don't know what to do anymore.
It also may be cowardly but I do not want to talk to either my parents, him or a therapist about this. At least not anytime soon. I couldn't bear to look myself in the mirror if I did.