i play multiple manual toons on multiple machines and different tools on others. I also play with my buddy and his set who do NOT use mq, with each of us controlling at least 1 toon in each of 2 groups, and the bulk in 1. There are some things i change because he's more anal than i am, or he pulls or tanks differently , like i wont use my rgmercs on bard because it doesnt act remotely like any real bard ive ever seen and he kept telling me your melody stopped or why arent you using this or that song (things that i always do when i play the bard myself, but hes a much better bard so he notices, i dont) I also dont play with zerkers myself, havent levels mine up yet, but where i have a pair of rogues, he has a pair of zerkers and our 2group lesson burns for the alts mt druid spamscasts heals at him, but i dont feel like finding and fixing her ini or creating conditionals for zerkers til i play with them regularly, and im not about to heal manually with her- if i want dedicated heals without mq, i pop a merc or invite one lol.
Playing with multiple people in the same group really only gets affected by their classes you may not encounter often, or their expertise on a class you have little knowledge or attention for- and in that case it wouldnt matter if its you and your brother and youre open about usage/both using. For recurring events like this you may want to have multiple setups for some toons, or just add some extra conditionals once you see what is and isnt annoying or intrusive. Their presence isnt going to make your group stop working so long as youre not running stuff like posse OR you keep your friendlists etc updated for it, etc. MQ isnt an all or nothing setup. you can use as much or as little as you want, its up to you. Some people even use it to raid, with raid guilds not just their own accounts. Unless your brothers an antiboxing nazi, i wouldnt worry.