I, too, am searching for info on David Blair Knox. He is also my third great grandfather. The Cleveland Genealogy says his parents were Adam and Charity Tripp Knox. I find no records to verify that. Also, I have a very old document found in family papers listing up to the third great grandparents of Hannah Louisa Knox Darrow. This paper says David's parents were Nathaniel and Thursy Ann (unknown) Knox. Have you ever been able to figure this out?