Complex sentence: He remarried in 1811 Emily Douglas, daughter of Archibald Douglas, and widow of Joseph Leeson, by whom she was the mother of Joseph Leeson, 4th Earl of Milltown, and had three more children, including Edward, 3rd Baron Cloncurry.
Split into simpler sentences: He remarried in 1811 Emily Douglas, daughter of Archibald Douglas, and widow of Joseph Leeson, by whom she was the mother of Joseph Leeson, 4th Earl of Milltown. They had three more children, including Edward, 3rd Baron Cloncurry.