RSS prefer to recruit kids as they question less and follow more.. You need to talk to your brother regularly, tell him how having questions in mind can make him avoid the biases and differences that they might teach. Show him real examples from your/his friends (from school or coaching etc.) where people from all communities are friends and good at heart.

Unpopular opinion here, but there are few shakhas which sticks to basics.

e.g. the one which my father's uncle used to run is still doing some good social works like - managing/funding schools, weekly stadium cleaning and exercises, monthly blood donation camps, free cataract surgeries, collecting funds and gathering youth.