Contrary to what the earlier posts may suggest, my direct line of Mathis' (James K.) does not relate genetically to Britton Mathis. I don't know about his cousin, John F or T Mathis.
I sure was disappointed to learn that fact.
My brother does match a Mathis line in McNairy County, TN and a Mathis/Mathews line in Jackson County, AL.
Georgia Mathis Cummons