He was a son of Nathaniel Coffin, Cashier of the Customs, and a brother of Admiral Sir Isaac Coffin, of the Royal Navy. A warm and decided Loyalist he volunteered to accompany the royal army in the battle of Breed's or Bunker's Hill and soon after obtained a commission.
He retired to New Brunswick at the close of the contest, with the rank of major, and received half pay. In the war of 1812 he raised and commanded a regiment which was disbanded in 1815.
He died at his seat, King's County, New Brunswick, in 1838, at the age of eighty seven.
Notwithstanding his choice of sides in the Revolution, he never lost his interest in the "old thirteen," and he remembered that he was "Boston born," from first to last.
Coffin family chart from The Baronetage of England, Or the History of the English Baronets ..., Volume 5, By William Betham. John Coffin was the son of Nathaniel and Elizabeth (Barnes) Coffin.