I can't vouch for the research behind it, but a family tree posted on ancestry.com lists his great-grandfather as William Henry Sledge who appears on the 1860 census in the northern division of Sumpter County. It has the following attached:

Name: W.H. Sledge
Side: Confederate
Regiment State/Origin: Confederate Troops
Regiment Name: General and Staff Officers, Corps, Division and Brigade Staffs, Non-com. Staffs and Bands, Enlisted Men, Staff Departments, C.S.A.
Regiment Name Expanded: General and Staff Officers, Non-Regimental Enlisted Men, CSA
Rank In: Surgeon
Rank In Expanded: Surgeon
Rank Out: Surgeon
Rank Out Expanded: Surgeon
Film Number: M818 roll 22