William Hayley was mentioned in his grandfather’s will as a grandson, but the name of his father was not given in that will. He is believed to have been the son of Holliday Hayley on the basis of Northampton County transactions:

5 Sept 1796: Deed of Gift of some negroes from Holiday Hayley to Wm. Hayley, both of Northampton county, N. C. On the same date, deed of gift from Holiday Hayley of Northampton Co., and James Hayley of Greenville Co., Va., of some negroes to his son, Holiday Hayley of Washington Co., Ga.”3163