I also research this line. I have little information on Obediah Ferguson, Sr., and it is hard to prove. I have Joel Ferguson, Sr. b. abt. 1729, d. 11 Sep 1788 in Lunenberg Co., VA, age 59 years. His wife may have been Catherine Joicy, but that is not confirmed and is only a clue.

Joel Ferguson, Sr., may have had three sons: Thomas, b. abt. 1753 in Lunenburg C., VA; Joel, b. abt. 1755 in Lunenburg Co., VA, and Obediah, b. abt. 1761 in Franklin Co., VA. A daughter Catherine may be part of this family, but not confirmed.

Obediah Ferguson, Sr. was born bet. 1761-1765 in Franklin Co. VA. He died before 15 Feb 1847 in Wallen's Creek, Lee Co., VA. His will was dated 1842, so he died after 1842 and before the date of the will.

Have you located his will and other available information on the web? I have little to help with, but would be glad to help collaborate.