Stuttering can be caused by trauma (aka neurogenic stuttering), either mental/emotional or stroke/TBI, but that is much less common than neurological/genetic ("normal" stuttering). Depending on the study, the stutter is more often than not hereditary (42%-85% with an avg of about 70%). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5370225/ I would also question your assertion that it is "a brain thing that I can't fix." No matter the underlying cause, you absolutely can work on it and modify your speech production and disconnect the baggage associated with it. The human brain is pretty plastic, especially when young. The Brain that Changes Itself is a fascinating read, if you are into that kind of thing.