Nancy died Dec 17, 1910 in Jones Co. MS.
She is indeed related to Clarke County Young's (in my opinion). She is in 1870 Clarke Co. with her mother Sarah in household, and also Hiram Adams (son of Epsy, her sister) next door. The spelling of Duval is so varied it is very hard to find in census records through search engines.
A James Dumont Duval died in Sunflower Co. MS, Dec 28, 1928. Not sure where either of them are buried. Hope this helps.