Complex sentence: The elder, Louis, Duke of Brittany, the latest in a series of Dauphins, succumbed on 8 March, leaving his brother, the two-year-old Duke of Anjou, who was later to succeed to the trone as Louis XV.
Split into simpler sentences: The elder, Louis, Duke of Brittany, the latest in a series of Dauphins, succumbed to it on 8 March. The only one to survive was the two-year-old Duke of Anjou, the future King Louis XV.