When Barnard Preston was born on 13 January 1727, in Baltimore, Baltimore, Maryland, United States, his father, James Preston, was 46 and his mother, Sarah Scott, was 36. He married Sarah Ruff on 28 December 1748, in Baltimore, Baltimore, Maryland, United States. They were the parents of at least 4 sons and 3 daughters. He died after about 14 October 1794, in Harford, Maryland, United States, at the age of 67, and was buried in Christ Church Cemetery, Forest Hill, Harford, Maryland, United States.