At the Breckinridge County Courthouse I found proof that Joseph Mason's wife was Jane Henderson. Jane's father Samuel Henderson died and left land in Franklin County, Virginia. In Deed Book A. page 493, is a legal document transferring Power of Attorney recorded 15 October 1809 whereby "Joseph Mason and Jane, his wife, late Jane Henderson, of Breckinridge County, Ky." appointed "Samuel Mason their lawful attorney, to ask and receive what they are entitled to from the estate of Samuel Henderson, deceased, who died Franklin County, Va."
https://wckyhistory-genealogy.org/wp-content/uploads/2021/07/Jerry-Long-Mason-John-died-1761-Correspondence.pdf