In 1799, Templeton married Katherine Johnson of Seymour Hill. Her family had been touched by the United Irish rebellion the previous year: her brother-in-law, Henry Munro, commander of the United army at the Battle of Ballynahinch, had been hanged. The couple had five children: Ellen, born on 30 September 1800, Robert, born on 12 December 1802, Catherine, born on 19 July 1806, Mary, born on 9 December 1809 and Matilda on 2 November 1813.