I'm assuming you are asking about William because you've already traced Clemmie and her family on earlier Erath Co, TX census records.This looks like William Marion, "N" on one census, but "M" on the other one.
1880 census Erath Co, TX:
Category: Name;Relationship to head of household; Marital Status; Gender; Race; Age; Birthplace; Occupation; Father's Birthplace; Mother's Birthplace.
William N. SPARKSSelfMMaleW44TXFarmingSCNC Martha E. SPARKSWifeMFemaleW40TXKeeping HouseSCNC William N. SPARKSSonSMaleW19TXWorks On FarmTXTX James H. SPARKSSonSMaleW13TXWorks On FarmTXTX Sarah I. SPARKSDauSFemaleW11TXTXTX John A. SPARKSSonSMaleW9TXWorks On FarmTXTX Martha A. SPARKSDauSFemaleW7TXTXTX
1870 census Rusk Co, TX:
Sparks, William D., 31, b AL - land 800/personal 200 " Martha J., 29, b AL " James H., 10, b TX " Mary L., 3, b TX " William M., 8, b TX " Sarah E., 1, b TX
1860 census Rusk Co, TX:
Sparks, Wm. D., 22, b AL - land 120/personal 100 " Martha J., 19, b AL " James H., 5/12, b TX
Sparks, Danl, 54, b SC - land 480/300 " Lucinda, 46, b SC " Charles, 18, b AL " James, 15, b AL " Polly A., 4, b TX Grigsby, M.S., 6, b TX (female) [I would say these are parents and family of William next door.Land and probate records should show who the heirs are.]