Don't have any tips, just wanted to say this is my experience too, but maybe not because of familiarity but preparedness. The more prepared I am the more I'm likely to stutter. Like if I'm the one actively approaching my family to tell them something, meaning I've rehearsed the content in my head, I'll stutter. If they approach me suddenly while I'm playing games, no problem. If a stranger suddenly approaches me to ask me something, no problem. If I'm ordering food from a stall, big problem regardless of whether I know the owner or not. The exception I have is talking to big crowds. I'll be prepared but not stutter. Maybe because I pretend I'm just talking to myself when I'm presenting or they're not even listening.