Have you ever considered talking to your brother about it directly? By doing so, you would not necessarily feel the need to talk to your parents about it. I know you're young, and may need the support of your parents, and that's okay too, i'm just thinking that maybe you and your brother could have a heart to heart and maybe find closure yourselves. In order to not have him automatically deny it though, you would need to approach this as a definite, that you definitely remember him doing this, and pose it more in the form of wanting you both to be able to find closure to this unfortunate incident. He may have been dabbling in smoking weed or something and was not himself. Did he drink or smoke dope or other drugs, do you know at the age he was when this occurred? I find that healing occurs most often between the people that incidents of abuse occurred. Think about this as one option.. Another of course would be to talk to the family, but it is you and he that need healing, not your parents.