Bliz, bunny is right - you have to let go of wanting a specific outcome, because you're in a toxic hostile situation.
That being said, is your brother super-countersuggestible? Is it really really obvious with him that he decides what to do by finding out what you want him to do and then picking the opposite choice on purpose, just to rub your nose in his refusal to listen to you?
With these types, the mere fact you want an outcome will be their reason for opposing it. They are incredible about that... if it's a choice between doing the smart thing and doing the mean thing, they'll go for the mean one, every time.
If he is that bad, don't tell him you have his number. If he's really dumb enough to go against whatever you advise as kind of a kneejerk reflex response, tell him to do the thing you least want him to do. [Don't throw me in that briar patch, Brother Fox, oh please, boo hoo hoo, said Brother Rabbit...]
But again, don't hope for too much. The countersuggestibility thing only works when they are so stupid, and so mean, that they can't stop themselves. If they're bright enough to realize you've figured it out, they may just change their game. Plus, it's manipulative even if it's in a good cause, and you may feel icky doing it.
Complete disengagement - just presenting the facts without advising any conclusion - may be the best way.
Good luck. What a jerque.
