He might be suffering from conduct disorder or oppositional defiant disorder, we need to check for other symptoms like lying, stealing, harming others, rebel behavior etc and also understand what does he think about what he is doing and why? Consulting a child & adolescent psychiatrist seems to be the best way to establish the diagnosis and move ahead with the treatment as suggested.

consult a psychiatrist for detailed evaluation & diagnosis.

U need to take your brother to consult a psychologist for behavioural therapy this will help your brother to get rid of problem.