Hey man, I’ve been through stuttering too. My fluency has drastically changed over the years from not very fluent to year after year more fluent. One thing you cannot do is label ur friends kid as a stutterer that will be ‘life long’ that isn’t true. I have found the more confident I am the less I stutter. He will need to find a way to be more confident and have friends but also to do some sort of speech therapy (if u want u can dm me).