I Y-DNA matched on FTDNA with a Pettit descendant of George Pettit (b. 1775, Kentucky; m. Elizabeth Gillespie). He believes George was the son of Thomas Pettit (b. 1755; m. Rachel Monroe). Our results show we’re in a completely different haplogroup from the Pettit-Mellows line.
He’s currently waiting on his Big Y-700 results, but based on current data he’ll likely fall under I-FT384455 unless a new downstream branch is identified.
(Edit: I realize you may have been referring to Thomas Pettit (b. 1663; m. Rachel Wilson) or his father. His documented line does trace back to that earlier Pettit family.)
I’ve also matched a couple of other Pettits who descend from Benjamin Pettit and Elizabeth Sprinkle.
Hope this helps clarify things!