I understand what you mean by little brothers like to mimic big brothers, but it is up to you to explain to him that he is not you. He has his own name, he has his own playing style, he much choose a nickname for himself. I am a bit annoyed by all this hate going around against you without any evidence or proof. Can you tell us how old is your brother so he has skills like you but he still doesn't have his own nickname? And when did you create your accounts? But that's not important. I have two pieces of advice for you:
First - explain to your brother that this is important and ask him to delete his account and make a new one with nickname he chooses/wants/likes to use (I have been Zax/Electric_Zax for over 15 years and many friends call me by that nickname).
Second - if you are a multiaccounter be fair and admit it. Delete your second (third, forth, etc. accounts

) account and if you want to play this much - buy some games. They are not as expensive as it may seem. Or at worst use the
French or the
Spanish server. You are allowed one account per server.