I’ve always had a more severe stutter around my parents and siblings. I don’t fully understand why, but I can assume it’s a comfort thing. They know how I talk and I may subconsciously not feel like putting in the extra effort to correct. For example, I’ve noticed I use replacement words less often for words that I feel I will stutter on. I’ve also heard the exact opposite as some stutter around strangers and hardly at all around close family. One of the many great mysteries around stuttering.