Complex sentence: His father had become a minor favourite of Louis XIII, who was addicted to hunting, and made him his Master of Wolfhounds before giving him his Dukedom when relatively young; he was 68 when Saint-Simon was born.
Split into simpler sentences: His father had become a minor favourite of Louis XIII, who was addicted to hunting. Louis made him his Master of Wolfhounds and then gave him a Dukedom when relatively young; he was 68 when Saint-Simon was born.