Hey,
It's great that you and your brother are playing PRO together and I hope you have a great time!
Unfortunately as of now, as far the rules regarding multiple accounts concern, we unfortunately have difficulties discerning whether 2 accounts are owned by one or two people if you play in the same domicile.
Are you and your brother playing in the same household? If yes, then I'm sorry to say that the system might consider you both as two accounts owned by one person, and so the standard rule concerning PVP on multiple accounts owned by the same person apply in this game. Of course, if your answer was no and you live in different houses and don't play under the same network or devices, then there would be no issue!
Right now, the rule over one person wanting to play PVP on more than one account is as follows:
This rule, and others, can be found on the PVP rules found here:
https://pokemonrevolution.net/forum/topic/31283-ranked-pvp-rules
I want to mention further that we do not endorse sharing accounts in any way! If you are detected playing on more than 4 accounts whatsoever, you should expect a ban after which you will need to appeal your case. Please refer to the overall game rules here:
https://pokemonrevolution.net/forum/topic/108815-overall-game-rules
Is there any specific thing you are worried about, or specific question you'd like to ask?
Ayroo