The will of Bethuel Barnum was dated 6 Aug 1787, proved 20 May 1788 (Wills, County of Albany, New York, vol. 1, 1787-1803). It shows oldest son William, son Bethuel, son Israel, daughter Rebecca, daughter Mary, and the heirs of daughter Anna. He gave to Mary Magee 5 Pounds, and to George and Bethuel Magee 5 shillings each. Bethuel, son of Bethuel, was named administrator when the executor named in the will refused to serve.
Both the Genealogical Record of the Barnum Family and The Barnum Family (both editions) suggest the possibility of an additional Bethuel Barnum between Bethuel Barnum (1705- 1787) and his son Lieutenant Bethuel Barnum, but I have not found reliable evidence to support that contention. His surname also appears written as Barnam.
In addition to the wife shown here, The Barnum Family (both editions) shows him married to (1) Annie Goodsil and (2) Phoebe Kelly. Other sources show only one wife, but mention Anna Larrabee Goodsel and Phoebe Kelly as wives of two of his grandsons.
Information obtained from Vol. II DAR Patriot Index pg. 12: He was a Private from New York. Will probated May 20, 1788, Surrogates Court, Albany, NY.
The Genealogical Record of the Barnum Family shows Anna Goodsall married to Jabez Barnum, the grandson of Bethuel. Descendant Lew Barnum has stated that he strongly suspects that is correct, since their eldest son was then named Abram Goodsall Barnum. It is also possible, of course, that there were two women named Anna Goodsall. The Barnum Family (both editions) gives him a birth date of 17 Feb 1716.
The Genealogical Record of the Barnum Family provides a death date of Oct 1885, an obvious error, since that would have made him more than 169 years old at the time of his death.