I saw news there was ban wave, and I have been banned for reasons I don't really know. I didn't use cheats on grand arena or normal arena, don't make any argues or insult someone, just log in game tod...
You could have spent the gear on the prereq toons to avoid getting caught as a cheater and to erase some of the advantage "your brother" garnered for you. But you didn't, so it seems you have enjoyed your ill-gotten advantage.