Hello Mr Antonio,
Yes, I have looked for a death certificate but I have not discovered one for Rueben yet. I really do not know but this family was about the same in 1880 but Gus(Augustus)and his family was living a couple door up. This is the entry for the household of Isaac & Gus Tilman:

1870 Census Saluda Division, Edgefield, SC
Isaac Tilman 48 Martha 40 Gus (male) 17 George 12 Uriah (male) 10 Bryant 8

1880 Census: Pine Grove, Edgefield, South Carolina
Jsaac Tillman 58 Martha Tillman 50 George Tillman 19 Bryan Tillman 17 Lizie Tillman9
Augustus Tillman 25 Lalla Tillman 19 Florance Tillman 1 Adalee Tillman 3M

Please continue to assist finding Isaac, Rueben, Jeff, Robt in 1870, I would truly be glad.