It’s not a theory, it’s true, most stuttering is genetic, with some cases of mental or physical trauma. My immediate family has 4 different members that stutter, I don’t even know bout family members I’ve never met, but it’s kind of a shame how strong the gene gets for families, I hope my kids don’t have to go through it as well, but of course I’m going to be as supportive as possible if they do. Side note, guys are 10x more likely to stutter than girls, so if you have a girl you should be safe.