It is Sarah Kavanaugh, younger daughter of Philemon Sr. and Sarah (Williams) Cavanaugh who is rumored to have married Charles Duncan. She, however, married Francis Stother, and she died long before the Sarah (?) Duncan who is buried on the Meadowbrook Farm at EKU in Madison Co., KY.
Philemon's son Philemon married Ann Cave. The two Philemon's are often mistaken for each other.
To my knowledge there are no surviving marriage records for the children of Philemon Cavanaugh Sr. It is thought that he gave a gift of land to each of his daughters as they married. The staggered dates of those deeds suggests that this is probably so. Sarah, however, was one of his minor daughters at the time of his death, so her land was given to her through his will. It is a lawsuit over her inheritance that proves her marriage to Strother rather than Duncan.
I decend from Charles Cavanaugh, elder brother of Sarah, and his wife Ann Covington, through their son William Kavanaugh, who was Isaac Duncan's father-in-law.