From Chalkley's Chronicles: Page 528.--12th August, 1772. Robert Stephenson's will--To wife, Martha; to son, Thomas, all lands; to each of living daughters, $1; to "my Mary Rankin, my daughter-in-law"; to grandchildren and Mary Rankin. Executors, John Polock and James Allen, Jr. Teste: James Anderson, Joseph (his mark) Reaburn, James Allen, Sr. Proved, 18th August, 1772. James Poage ("executor therein named") and James Allen qualify with Jno. Anderson, James Allen.
Mary Rankin was a daughter of George Rankin and Martha Crawford.After George Rankin died, Martha married Robert Stephenson.I think George and Thomas Rankin were brothers.
1785--September 5, John Young and Mary Rankin; surety, James Rankin (her brother).
The George Poage that you mention was probably the son of George Poage that married Rachael Stephenson, daughter of Thomas Stephenson and Rachel ?.