He married Agnes De Adrerne. Agnes was born in Alford, Lincoln, Eng about 1276. Agnes was the
daughter of Peter De Aderne and Margery De Aderne MRS.
William was baptized a member of The Church of Jesus Christ of Latter-day Saints February 6, 1974. Temple Code: PV. He was
endowed February 16, 1974. Temple Code: PV. He was sealed to his parents March 5, 1974. Temple Code: PV.
William De Mainwaring and Agnes De Adrerne had the following children: