I assume E P Petty, the putative father of George Petty, is Elijah Parsons Petty? Far from being his father, he actually happens to be George's grandson! As a rule, middle names were rare before the Revolutionary War.
The father of George Petty is James Petty. The mother is indeed Martha Clanton.
The will of James Petty, as abstracted from the Petty Papers, vol. 12, n. 2, p. 16:
Union Co., SC Courthouse, Box 5, package 3: Will of James Petty dated 14 March 1806, proven 3 Nov 1806, mentions wife Martha; Children Ambrose, James, Absalom, Joshua, Thomas, George, Rachel, Sarah, Martha, Catherine, Polly, Gabriel. Witness Charles Petty, John Petty.
Starting from the Ancestral File BVLS-9T quoted as a "source", I find George Petty's father to be E P Petty (GC6J-MB). Then I find that E P Petty's parents are listed as Thomas Petty (207W-CD) and Katherine Garton (GQN3-DJ). These happen to be the parents of James. There is no "E P" in this family according to Thomas' will.
Will of Thomas Petty abstracted from Petty Papers, v. 1, n. 2, p. 23:
Dated 31 Jan 1748/9, names wife Katherine already dead, most of his children had already received their shares. Gave each of his married children, namely, John, Thomas, Christopher, William, James, Rebecca Sims, and Mary Knight only one shilling. To other 2: George and Martha he split the remainder. Probated 24 May 1750.