First of all, as far as you know, nobody in your family stuttered. I only found out two years ago that my dad stuttered. I'm 27 and he left when I was 15. He always carried a lot of shame and told me that he never felt comfortable talking about it, even though he raised me and saw how much stuttering affected my own life. So you never know if someone in your family might not have told anyone. Second of all, just because you didn't inherit it from someone, doesn't mean it's not genetic. Take something like schizophrenia for example, which is well researched in twins that were separated at birth. They found that if one twin had schizophrenia, the other twin (who grew up in a different environment) had between 50-80% chance of developing schizophrenia. So obviously there was a genetic link. Yet, many people develop schizophrenia without having anyone in their family with schizophrenia. Does that mean it's not genetic? No, it just means that we don't fully understand it. Genetics is very complicated