Are you thinking the Robert Adair in these recent posts is the same one mentioned in Chalkley "Chronicles of the Scotch-Irish Settlement in Virginia"?
He (maybe the same Robert?) shows up six times between 1755 and 1767 that I'm aware of:
Vol 1 p. 72,March 19, 1755 - Robert A'Dair convicted of threatening to favor the inroads of the enemy Indians
Vol. 2, p. 417, 1755 - Robert Breckinridge's list of delinquents in the tax levies includes Ro. Adear, no estate.
Vol. 3 p. 84 August 30, 1759 - James Robertson's estate sold at vendue - purchasers include Robt. Adair
Vol. 1 p. 91, August 18, 1761 - Robert Adair appointed Constable in Staunton, vice Samuel Cloyd
Vol. 1 p. 100,August 21, 1762 - Israel Christian released to George Wilson his interest in a bill of sale now on record to him from Robt. Adair
Vol 3 p. 102, November 24, 1767, James Hughes estate settlement recorded, among "bills due the estate that are doubful," Robt. Adair's.
Also, from Shirley's Adair rootsweb post 11 Sep 2002
"Robert A'Dair, Augusta co. VA 1762 18 Feb 1762 John Pharris (Farris ?) Plt. against George Anderson Deft - An Attachment Robert A'Dair a Garnishee also in this Court disclosed that of the Estate of the Defendant he had Suspicionds(?) for which he has been in Execution VA, Augusta Co., Court Order Book 7, 1761-1763, p. 160"
He is listed various places as being in Captain George Wilson's Company, August 11, 1756.There are five Millers on that list:James, John, Patrick, Valentine, and William.
What is the source of the information that the S. C. Robert Adair came from Virginia?
It's interesting that in the 1820 SC census cited above Elisabeth is shown living with 12 free colored persons - I'm not familiar with SC history, but in Virginia and Tennessee a free colored person is anyone who is not white - and could be used for free mixed race persons, including Indians.
I had been eyeing the Chalkley Robert as a father for my Montgomery Co. James Addair (born about 1750), but am willing to share;-)