A borther of Increase Mather appears to have married a Mary, and Nathanial, as he was in London, appears the most likely brother. Mary Benn was the daughter of the Revd. William Benn of Dorchester.
In 1699, soon after Nathanial had died (in 1697), Mary Mather of London, Widow, wrote her Will, dated 29 April 1699 (with later Codicils added in 1699 and 1705). She gave £25 to her "Brother-in-Law Mr Increase Mather, his Execurors or Administrators". Alos Mary Mather bequethed one part of her estate "to Mr Wareham Mather, son of Mr Elizar Mather deceased"