My mother swears up and down that I started stuttering when my sister (two years younger than me) started to talk. So I would’ve been between 4 and 5. My dad was a stutterer too, so some therapists thought it might’ve been “learned” behavior: and tried a course of negative reinforcement to break me of it. No dice. But I have some stories that make current SLP students gasp in disbelief when I tell the story.