not sure if this will help but i think it's because of the fact that his family already knows about his condition so he won't have to feel as nervous when talking... like he consciously knows that they won't judge him. when encountering a stranger, he doesn't want to give off a bad impression so he becomes mentally aware and stress on how he'll talk... resulting him to stutter
I have also another condition that gets triggered when I'm with people I don't know or in public transport. However when I'm with my family, close friends or alone I have it under control. It's mainly because I have told them what I have and I don't feel judged with them.
so I've got a question about the whole stuttering thing. I would understand the whole thing exept he doesn't seem to have a problem stuttering around his family. Which confuses the hell out of me. If its not "I'm stuttering because I'm nervous" then what is the reason for that?