Mariah Creek Christian Church Cemetery, Mariah Creek, Knox, IN - This Cemetery is in the churchyard.

Thomas and Mary Duncan Piety
Thomas Piety Sr.
Thomas Piety militia plaque under stone 1   2
Mary Duncan Piety
 
Thomas Piety, Jr. (brother of James Duncan Piety)
Samuel Piety - Brother of James Duncan Piety.  Mary Piety was living with Samuel in the 1850 Census of Knox County.
 
Jonathan Polk, Mary Polk, and Harvey Polk - Thomas Piety's mother was Sarah Polk.  These may be related, although I don't know a connection.

Mariah Creek Cemetery entrance - Thomas and Mary (Duncan) Piety are on the mound (near right-center)