Perhaps William was son of Sam & Ann Adair ? Marriage records of New Castle: Samuel Adair to Ann Eakin 10 March 1760.
Samuel Adair, will, May 11 1773, probated New Castle, Delaware.
Children 1. Mary Adair bc1762 2. Samuel Adair jnr. bc1764 m. Margaret Eakin 3. Joseph Adair snr. b. Nov 12 1766 Cecil Co. MD (same as New Castle Delaware) d. Aug 15 1832 Jackson Co. Missouri 4. Dorcus Adair m. Thomas Price 5. John Adair m. Eliz. Sinno 6. WILLIAM ADAIR??