This actually happened in my family and is also the reason I got screwed haha. My father, brother and an uncle all stuttered in early age but around 13-15, they all grew out of it and are completely fluent now. My stutter was mild to slightly severe when i was younger but i never grew out of it and it's been getting worse the past couple of years. Tried therapy this year but to no avail. It's very severe now and most doctors said that it would've been more beneficial if i got help at an early age.