I do the same with my family, I stutter the most with them, something I was asked one time was “do you stutter the most with them cause you’re more comfortable with them?” And that got me thinking, maybe I do stutter with them cause I’m so comfortable with stuttering around them, cause when I meet someone new I don’t stutter a whole lot cause I can usually hide it with new people at first then when I get to know someone better my stutter comes out more.