I think that your UH Nixon may be Udolphus Hamilton Nixon? b 1864 in Campbell Co, Ga., d. abt. 1903
According to newspaper articles of the time, he: medical missionary to Monterrey helped build a hospital there had a dtr, Irene, who was a Methodist minister had brother William Dawson Nixon had brother Farmer Moses Nixon
According to other information, such as census and Bible records, etc. that makes him: son of James Hamilton Nixon, b. 1830, d 1888 married Susan Emily Davies 6/20/1833 - abt. 10/27/1890 son of John Wallace Nixon and Ellenor/Ellender Jones.
I am descended from James Hamilton Nixon, but from UHN,