Wayne (WayneLII at aol.com) said this about Nathaniel's mother, Catherine Britton:
I think that Catharine's mother was Mary Fountain. I found the baptism for Catharine and it has her birth as April 6, 1757. The church was St. Andrew's Church in Richmond, Staten Island ("Staten Island Church Records," by Tobias Wright, p. 247): born April 6, 1757 - parents Nathaniel Brittain & wife- child-Katharine. She had a brother, Richard: (p. 255): born March 22, 1766 - parents Nathaniel Brittain & Mary his wife- child-Richard.
The Britton genealogy gives her birth date as March 30, 1759 but says she died on Dec. 29, 1838 at the age of 79 years, 3 months, and 8 days. That would make her birth date Sep 21, 1759. Maybe the tombstone was misread.