You are probably descended from Timothy Dargan who was a 1722 resident of Fauquier Co., VA. I see by the follow up email to you from Shaw that they married into the Strother and Singleton families. These were also Fauquier families, some choosing to remain in Fauquier Co., while others journeyed south. My source for Timothy Dargan is the book, Northern Neck Warrents and Surveys by Peggy Shomo Joyner, Vol. III, p. 138. He lived off of Cedar Run in southern Fauquier Co, next to Charles Burgess, Thomas Stamps (who married into my Metcalfe line), Col. Thomas Harrison (desc. of immigrant Burr Harrison), John German(s), and Colclough (from Stafford Co., VA). There is a wealth of information online on the Strother family of Va (see records in King George Co., VA). Some other families of Pr. Wm. Co., VA (parent of Fauquier) also saw family members move south: Winn, Feagan, Botts, and Cantey.
I hope this helps! I always like to help someone when I can.