This is just my opinion but I went through the exact same thing and I know exactly why now. It sounds like your parents (and friends?) can be a little judgmental about the way you speak, and it sounds like they give you unsolicited advice. This will make you more anxious when talking to them, and it’s like a vicious cycle: the more your parents say things, the more anxious you get and the more you anticipate you’re going to stutter, and then you do stutter more. When you’re with a stranger, it’s a blank slate. They have no idea you stutter, and you don’t have to worry about preconceived ideas about you. When I was in highschool, I went through the same thing. I would stutter more around my friends and family than strangers because honestly I felt judged by the people In my life. When I met my boyfriend in college (we’ve been dating for 5 years now) he was the first person to not care, and accepted me 100%. I never really stutter around him anymore. I have built so much confidence since I was in high school and stutter significantly less than I did before. I do still stutter around my parents though, but that’s because they’re the only people in my lives currently that I feel judged by. Please PM me anytime with any questions or if you just wanna talk, I’ve been in your shoes once :)