When Thomas Coulsen Gregg was born on 9 May 1794, in Loudoun, Virginia, United States, his father, Thomas Gregg III, was 32 and his mother, Sarah Coulson, was 29. He married Mary Brown on 27 November 1817. They were the parents of at least 2 sons and 6 daughters. He died on 9 July 1878, in Bellville, Richland, Ohio, United States, at the age of 84, and was buried in Perrysville Union Cemetery, Perrysville, Ashland, Ohio, United States.