First of all, you need to learn to forgive yourself. Were you abused like your brother was? Perhaps you were simply doing that to your dog to cope with your own pain and abuse...its amazing what humans do to survive their environment...i feel bad for the dog..however its over with now and you realize it and hopefully your getting help and i know that your a good person...dont feel so bad...i would speak to someone professional about that...perhaps you felt if you did that to the dog you were somehow taking away pain from your brother? It sounds weird but its like a validation..remember you dont have to answer these questions out loud since they are inimate and personal but just think about the relativity...and pm me if you need to talk...no worries..i support you and i know you were only alittle boy..you have to forgive yourself for this...good luck
inny