The cause of stuttering is part genetic and part genetic. For each person, it might be more genetic than env, or vice versa. For me personally, I was told by my parents that I started stuttering pretty much as soon as I began speaking at age 2. So mine is more genetic, plus pretty much everyone born from my grand-mother' on my dad's side has it. The only people children who don't stutter are kids my grand-mother had with a different man. which means who you have kids with can cancel out the stutter gene. You also may have a parent or ancestor(s) that stuttered but you're unaware of them. Also other genes can cancel out others or cause them to express themselves differently than another person who has the same gene.