I just now found your message. I don't recall hearing of your family and don't know how your pedigree fits to mine, but Prestonburg is the right area. I've been there visiting relatives. I grew up myself in Iowa so don't know many from the area personally. When I was old enough to notice my cousins spelled their names Thornsberry, my dad said the armymisread his birth certificate, which was handwritten, as Thornsbury and made his army papers that way. As those army papers legally changed the spelling of his name, my dad said he'd have to go to court to change it back and he never felt it was worth the money to do it.