Complex sentence: He was an officer in the Royal Navy, marrying Mary Hathaway, the widow of Southwark merchant James Thomas Hathaway and eldest daughter of John Kennedy of Sutton Coldfield.
Split into simpler sentences: He was an officer in the Royal Navy. He married Mary Hathaway, the widow of Southwark merchant James Thomas Hathaway and eldest daughter of John Kennedy of Sutton Coldfield.