Hi there ,
Welcome to Just answer !
Well, it seems like your brother could be suffering from what is called as Social phobia or Agoraphobia , which makes a person shun away from meeting people who are strangers and wants to remain in the confines of his own home in the company of his known people ..
So, i would suggest that he should be taken to a psychologist who after evaluating him would be able to confirm his diagnosis of social phobia or is it agoraphobia and once the diagnosis is confirmed the psycholohist will have him started on psychotherapy ( counseling ) and the best type of counseling for such phobias is called as Cognitive behavioural therapy ( CBT ).This therapy will help him to overcome his phobia of going out and meeting people ..and leading a normal life all over again.
see the link below for better understanding of agoraphobia ..
I hope this helps..
I wish you all the best..
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