Nathaniel Fillmore Jr. was born on April 19, 1771 in Bennington, Bennington County, Vermont, the son of Nathaniel Fillmore Sr. (1739–1814), a native and soldier during the American Revolution, and his wife, Hepzibah Wood (1747–1783). Nathaniel Fillmore Sr. was the son of John Fillmore Jr. (1702–1777), a ship's captain. John Fillmore Jr. was the son of John Fillmore Sr. (1676–1712), a native and mariner.