The marriage to Mary Whitcomb appears to be the father re-marrying, not the son marrying. In his accounting of his father's estate, this John has a charge "to the Widow my Mother mary More", indicating that his father's widow was named Mary.
See also, Source:Holman, Mary Lovering. Ancestry of Colonel John Harrington Stevens and His Wife, Frances Helen Miller, p. 91: "A Mary Whitcomb m. 23 Aug. 1683, John Moore, both of Lancaster; it is stated that she was the dau. of John1, but she may have been the widow of John2." It certainly wasn't the daughter of Job and Mary Whitcomb, that Mary only being born in Dec 1671, so not even 12 at the time of this marriage, and Job appears to have moved to Connecticut before 1679.