I'm the only person in my whole family who stutters. It's really weird, and makes it harder because no one really understands. A lot of my family has other anxiety related things, though, so that part is genetic. I once went to a stuttering group where one girl had an identical twin who was completely fluent. She said she avoided school presentations, etc, by changing clothes with her sister in the bathroom before the class, and then swapping identities. At the time I thought that was the coolest thing ever, but looking back, all that avoidance really isn't helpful.