Hi, Patrick!! I'm very hopeful that a descendant of the Gabriel Alexander who died in Augusta Co, VA bet Aug 1778 & Mar 1779 can be found to do a DNA test precisely to see if they would match your DNA results.
It's not finalized yet, but it appears that Oliver Alexander who resided in Augusta -- probably in the 1760/70s and later moved to Washington Co, VA -- is closely related, genetically, to the Seven Brothers/Two Sisters.Quite a surprising match!!
We never know how the DNA results are going to turn out.There have been lots of surprising matches AND non-matches.