In online databases, I have seen one other son for Tirzah & Richard - a William Davis.
Terzah Morrison, as heir of William Morrison, by deed on 6 Jun 1774, conveyed lands in Augusta Co - shown by a suit [Stuart vs. Duncan] in the Augusta count court 1808-1809.
Thomas Stewart and wife Terzah of Bedford Co deeded in 1807 to William Penn Jr. for 5sh, 56 acres of land in Amherst Co [DB K, p.548]. In 1815 they deeded land in Amherst to Roderick Taliaferro [DB M, p.85]
18 Dec 1837, Thomas Stewart of Bedford Co deeded to Nathaniel W. Floyd, admin of Charles Stewart's estate his $200 interest in the estate of their late brother, David Stewart, of Georgia, who had died without lawful issue. Thomas stated he was "representing my brothers and sisters both in Georgia and Virginia". Since it is known that most of Charles' & Thomas' siblings had gone to Georgia, as had their widowed mother, this effectively places Thomas Stewart in the family. The father, John Stewart, died in Amherst, 1784, naming his thirteen children, to include Thomas, Charles, David, etc. Several of the siblings married into the Floyd family, also "gone to Georgia".
Tirzah MORRISON and Richard DAVIS had the following children: