As some who stutters, I would advice few things. Let not anyone point to him that he stutters, you or the whole family. That creates negative impact on the children's mind and further increases the problem, I have faced the same thing. Never complete is sentences ever, give him time all the time he wants and let him express himself fully. He still is of very tender age, so he might not agree to speech therapies or even Stuttering Self Help groups ( which generally exist in all major tier cities.). So give him time, he will sometime in future you can bring up the idea gently and see if he is comfortable with it. Meanwhile you also do the research on what you can do from a family perspective. Important thing is that he needs a conducive and a relaxed atmosphere at home, where he never feels pressured or anxiety in expressing himself, that is really important. Personally, I was in the same boat, so I know how much valuable the family support and that environment means for ones growth. I would advice though search for Stammering Self Help Groups in your city, they are free self help groups, where people who stammer meet and express themselves freely, personally it really helped me a lot to gain confidence and become more relaxed. Probably sometime in future if he participates in stuff like this, he will grow and gain experience. Best of luck to you.