Kirk married Rachel Hughes, daughter of Elisha Hughes, of East Nottingham. They had nine children, Elisha (1775–1823), Jacob (1779–1841), twins Timothy (1781–c. 1839) and John (1781–1853), Josiah (1784–1821), Ann (1788–1816), Levi (1790–1814), Mary (1792–1857) and Lewis (1793–1825).[1] His son Timothy was a member of the Pennsylvania House of Representatives. His daughter Ann married U.S. Congressman Jeremiah Brown.[1] His son Josiah worked in management in flour mills, paper mills and a cotton factory.[2] His great-grandson Theodore K. Stubbs served as a member of the Pennsylvania House of Representatives.[2] The family lived on North East Creek.[1]