According to Josiah's death record on 5 Jan 1892 he was the son of Jos. and Mary Stewart.
His wife Lydia was indeed a Stewart and was the dau of Solomon Stewart and Dolly Gammon. Lydia died 25 Sep 1872.
Cordelia's father, Arthur Jackson Overton, was the son of Miles Overton of Camden County NC.
I'm interested in where the last name for Cordelia's mother came from :-) You stated in another query that it was Whitehead.