I am the only person in my entire family - including cousins, aunts, uncles - that stutters. I went to the NiH many many years ago to participate in a study on stuttering and they were flabbergasted as there is usually an adult in the family that stutters. In the end, I could not complete the study as I am partially deaf (did not know that prior). HOWEVER….. my mother had an incurable, degenerative disease that started showing symptoms when I was growing up. I have no memories of my mom doing mom things. So the assumption (huge assumption) is that I got it from her.