Complex sentence: In August 1672 he was married to Isabella, the daughter and heiress of Henry Bennet, 1st Earl of Arlington, and was created Baron Sudbury, Viscount Ipswich, and Earl of Euston; in 1675 he was created Duke of Grafton.
Split into simpler sentences: In August 1672 he was married to Isabella, the daughter and heiress of Henry Bennet, 1st Earl of Arlington. At the time of his marriage, Henry was created Baron Sudbury, Viscount Ipswich, and Earl of Euston; in 1675 he was created Duke of Grafton.