Most of my information earlier than 1900 has come from searching sites like Ancestry census and similar genealogy forums. I don't have anyone to query. THe line I'm following, I believe derives from William Berrian Cannady (1863-1920). I have him as a son of Solomon P.W. Cannady of Emanuel, GA. (1835-bef 1883). My son is a Cannady.
I'm not convinced from online data anyway, that the John who married Whitty is in the same direct line. I think there is a second John who is their son, who returned to SC.