I checked the SUVCW Ohio Dept Graves Registration database and found the following:

Amaziah Clark, 1840-1923, Corporal Co A 67th OVI
buried in Spring Hill-Tedrow Cemetery, Fulton County OH

Edgar Clark, 1836-1918, Private Co I 67th OVI
buried in Spring Hill-Tedrow Cemetery, Fulton County OH

By any chance do you have their complete birth and death dates?

Regards,

Kent Dorr
SUVCW Graves Registration
Ohio Dept