There are marriaged for William Isherwood and Mary Holt (farmer, 1818) and Mary Hardman (weaver, 1817) so which Mary? Hardman is a better fit as Jonathan born in 1817.
In 1841, Mary was alone (aged 40) at Duncar Fold, so it is assumed William had died. With her were Jonathan (20), Samuel (20), John (15), Sarah (15), Henry (13) and James (9).