I have information on Joseph Campbell Pettus' ancestors that indicate that it is incorrect to say that he was of Cherokee descent (but do accept that his two wives may have been of Indian descent).
Joseph Campbell Pettus was the son of James Thomas Pettus, born 2 Nov 1830 in York Co. SC. He married Mary Emeline Knox- I have no further information on her other than her father being named John Knox. Joseph Campbell Pettus died 8 May 1883 and is buried in Bethel Cemetery, York County, SC.
James Thomas Pettus was the son of George Pettus, b. abt. 1800 in York County, son of William Pettus, b. 1768 in Hanover Co., Va and of Mary Knox, b. 1770 in Mecklenburg Co, NC.William Pettus, d. 1818, was a member of the SC legislature and was one of the agents appointed as a commissioner to oversee the Catawba Indian Land. Mary Knox was the daughter of Samuel Knox and Mary Taggart Knox. Samuel Knox had the first recorded lease in the Catawba Indian Land. The lease was signed in March 1785 and was for 4500 acres north of Fort Mill. Actually it was the land north of Steel Creek to the NC line. Knox died in 1800. William Pettus, his brother Capt. George Pettus who married Jane Knox and Alexander Candlish who married Sarah Knox, the only three children of Samuel Knox and Mary Taggart, inherited the 4,500 acres. William Pettus and Capt George Pettus (1753-1816) were brothers and children of Stephen Pettus Jr. and Anne Dillard Pettus of Hanover Court House, Va. The family can be traced back to Norwich, England. There are plenty of sites on the net that have this family listed.