Sorry I'm a little late with the follow-up. the information given to me is this: Joab Mountacastle b. ca. 1700-1710 maiired Ann Duke, b. ca. 1702-1715, daughter of James Duke, b. ca. 1677 and Mary Byrd, b. Feb.1683. Date of the marriage was not given. They had several children; Mrs. Brandenberger apparently mentions them in her first Duke Family Book. A man named Eaton Nance witnessed Joab's 1773 will. I am planning to visit the Library of Va. in Richmond the week after Christmas and hopefully can find this book, or some other evidence to support this information.