Complex sentence: In 1809 Cockburn married his cousin Mary Cockburn; they had one surviving daughter, Augusta Harriot Mary Cockburn (d.1869), who married Captain John Cochrane Hoseason.
Split into simpler sentences: In 1809 Cockburn married his cousin Mary Cockburn. The couple had one surviving daughter, Augusta Harriot Mary Cockburn (d.1869), who married Captain John Cochrane Hoseason.