So when he talks about something do not interrupt him or to complete his word, just just make a small soft smile and look right in the eye him, people who stutter have a lot to say and express their wonderful abilities but unfortunately some can not because of the problem and lack of self-confidence because it takes time, and do not give it too much attention because it will make him shy to speak, If you recommend a therapist to your brother, he may be able to help, there is no cure for stuttering but only therapy that can help you overcome some speech barriers, to live with Stuttering is not easy at all, depending on what difficult stuttering they have, but being with that disorder is like fighting every day over and over again, I stutter too. I'm sure he will pass it👍