I started stuttering when i was 5 or 6 year old when my family was going to a wedding.The Doctor told my family that my Jaw muscles are weak and Now i just turned 18 and it has gotten worse since i turned 16 In my opinion your son can overcome it easily if guided by right people and doctors Note : one of the mains reasons for kid to start Stuttering is mental trauma or something like that before i turned 16 my Stuttering was hardly a problem but since i turned 16 i become more mature and Seeing my Parents argue and Curse each other and seeing my mother cry and seeing my big sister having health problem since she was 18 now she is 25 and Because of her Thyroid problems which also created the problem of Blood pressure rising and going down at such a young age gave me some kind of trauma that made my stuttering alot worse . Sorry if it is hard for you read , my English is not very good But i recommend never fight or argue with your wife infront of your children , Stuttering increases because of stress