So, you're telling me that your brother installed aimbot on your PC without you knowing? Any sibling would give a hint about what they have done even if they don't want to, it's natural.
Secondly, if your brother had installed it and you didn't want it as it would get you banned, why did you carry on playing with it on? I'm sure you would notice the difference immediately.
Anyway, you don't have to answer these questions. You will be unbanned in a months time, on the 18th of October. Don't join the server before this time as you will be banned permanently from the server. Similarly, don't use any hacks again after you are unbanned as it will result in the same punishment.