I experience something like this too! So when I‘m with people I just met, I tend to stutter less. When with my parents it‘s like a return to the old habits and stutter a lot. My therapist said it has to do with this ‚habits‘. As a child, when I spent most time with mom and dad, it was also when my stutter was at its worse but with new people it‘s like my brain can adapt better to the techniques I‘ve learned or I am just overall more fluent. Nervousness is although a big thing for me, when with my parents I‘m always quite nervous I‘ll stutter more and they‘ll just feel like I am a disappointment because after all this time, I still stutter.