The Genealogical Record of the Barnum Family shows David as an only child, while The Barnum Family, 1315-1907 provides the names of seven brothers. The latter source has apparently confused him with David (1740-1795), son of Ephraim, son of Thomas, son of Thomas Barnam. The Barnum Family also leaves out a generation in his line of descent, showing his sons David Barnum and Richard D. Barnum as the sons of their grandfather.
David Barnum was one of the first settlers of Danbury, and afterwards became one of the original three proprietors of Kent, moving there in 1752.