Thanks for your response. Here is a file on Reverend Alexander Davidson. The Caleb Davidson who you mentioned is included therein:http://homepages.rootsweb.ancestry.com/~genea/Dzalexellis.ht...
Reverend Alexander Davidson's father (who was also named Alexander) died in Spotsylvania Co., VA in the 1740s. Reverend Alexander Davidson was then in NC for a while, before settling in Barren Co., KY. This overall family has many DNA donors, and they are in "Family 8" at www.davidsongenes.org
. It APPEARS that one or more of the donors in "Family 8" do not descend from the Reverend, so they probably descend from one of the Reverend's brother's or uncles (and those other "branches" of the overall family have not been researched nearly as well as the Reverend's "branch").
Young Davidson came into Barren Co., KY from Campbell Co., VA between the 1820 census and the 1830 census. It is almost certain that Young Davidson was not a member of DNA "Family 8," and Young Davidson was probably a member of either "Family 7" or "Family 10" (who were both in Campbell Co., VA in the late-1700s and early-1800s....and there was also yet a third apparently unrelated Davidson family in Campbell Co., VA that was headed by yet another Alexander Davidson).
Note: One of my biggest surprises since I became interested in genealogy is that were about a DOZEN or more UNRELATED Davidson/Davison/Davisson families in just Virgina alone in the 1600s-early-1800s. We have identified as many as eight such unrelated families in just the Augusta/Botetourt/Rckbridge Co., VA area alone. DNA testing continues to prove what the documentation already seemed to suggest....that is, these families truly were/are not "related" (i.e., they do not share a common male Davidson/Davison/Davisson ancestor in any meaningful genealogical timeframe).
I believe that Young Davidson fathered a son who was also named Alexander Davidson, so one has to be careful not to "intermix" these two unrelated families. I hope to someday find a male Davidson who "traces back" to Young Davidson and who is willing to take the DNA test.