there is a reason why they say blood is thicker than water .... walk away now and save the pain .... but you won't
I doubt there's really anything you can do coming in between them is like asking for another headache
Maybe you should just point out the behaviors you dislike and describe how they affect you emotionally I wouldn't mention his brother that would probably only make him defensive
You're welcome best of luck to you all
Blow them both at once.