Complex sentence: His paternal grandfather, Antoine Philippe de Marigny, was a French nobleman, military officer, and geographer, while his maternal grandfather, Jean Baptiste d'Estrehan, was the Royal Treasurer of the Louisiana colony.
Split into simpler sentences: His paternal grandfather, Antoine Philippe de Marigny, was a French nobleman, military officer, and geographer. His maternal grandfather, Jean Baptiste d'Estrehan, was the royal treasurer of the Louisiana colony.