Personal life
In 1779, Duer married Lady Catherine Alexander (1755–1826), second daughter of Sarah (née Livingston) Alexander and Lord Stirling, a major general in the Continental Army. The marriage took place at Stirling's country seat, "The Buildings," near Basking Ridge, New Jersey. It was designed in the style of a residence of an English nobleman, with all the appointments of an English country seat. Catherine's paternal grandparents were New Jersey Attorney General James Alexander and merchant Mary Spratt Provoost Alexander, and her maternal grandparents were Catherine Van Brugh Livingston and Philip Livingston, 2nd Lord of Livingston Manor. She was, descended from the De Peysters, Livingstons, and Schuylers, and occupied a prominent place in the society of the period.
Together, they were the parents of eight children, including:
William Alexander Duer (1780–1858), who was a justice of the New York State Supreme Court, and for many years the President of Columbia University. He married Hannah Maria Denning (1782–1862), daughter of U.S. Representative William Denning.
John Duer (1782–1858), who was a noted lawyer and jurist of New York. He married Anna Bedford Bunner (1783–1864), sister of U.S. Representative Rudolph Bunner.
Frances Duer (1786–1869), who was married to Beverley Robinson (1779–1857), grandson of merchant Beverley Robinson.
Sarah Henrietta Duer (b. 1787), who married John Witherspoon Smith, son and grandson of Princeton Presidents Samuel Stanhope Smith and John Witherspoon.
Catherine Alexander Duer (1788–1882).
Maria Theodora Duer (1789–1837), who married Beverly Chew (1773–1851) in 1810.
Henrietta Elizabeth Duer (1790–1839), who married Morris Robinson (1784–1849), brother of Beverley Robinson and founder of the Mutual Life Insurance Company of New York.
Alexander Duer (1793–1819), who married Ann Maria Westcott (1808–1897), daughter of Col. and New York State Senator David M. Westcott, in 1815.
Duer died in New York City on April 18, 1799 at age 57. He was buried in the family vault under the old church of St. Thomas and was later reinterred in Jamaica, Long Island, New York. After his death, his widow remarried to William Neilson on September 15, 1801.
