Ancestral File has Sarah Dabney Johnston b. 29 Jun 1776, Spotsylvania, VA , died 1813. Her father is shown as Henry Goodloe Johnston b. 12 Apr 1727 Exxex, VA, he died 23 May 1802 at Spotsylvania, VA. His wife was Agnes Carr Waller b. Spotsylvania, VA 20 Jul 1736 died Mar 1831 Albemarle, VA.
Henry G. Johnston's parents were William Buford Johnston b. 1699 d 4 Jun 1728 and Mary Loodloe b. 1699, d. 21 Feb1732. Agnes C. Waller's parents were John Waller b. about 1701 died 6 Feb 1776. John Waller's wife was Agnes Mary Carr b. 30 Jan 1712, died 29 May 1777.