Complex sentence: He married Katherine Preston, daughter of Robert Preston, 1st Viscount Gormanston and had several daughters, and one son William, who married Margaret St Lawrence, daughter and heiress of Thomas St. Lawrence, Attorney General for Ireland.
Split into simpler sentences: He married Katherine Preston, daughter of Robert Preston, 1st Viscount Gormanston. They had several daughters, and one son William, who married Margaret St Lawrence, daughter and heiress of Thomas St. Lawrence, Attorney General for Ireland.