Had daughters Henrietta and Harriet (World Family Tree # 5738).
Ziebarth, pages 78-84 seems to confuse this John Magill with the one who went to Virginia. According to an outline tree John Ziebarth sent to me, the John Magill who went to Virginia was John H. Magill, son of Mary Magill and John Hawkins Magill (Ziebarth, John. Direct conections : Ziebarth-McGill ancestry. New York : Ziemag Publishing, 1997).