Complex sentence: Her maternal grandparents were Bernard de Saint-Severin, Prince of Besignano, and Jeanne Eléonore Piccolimini, descendant of King Alphonso V of Aragon and his mistress Giraldona Carlino.
Split into simpler sentences: Her maternal grandparents were Bernard de Saint-Severin, Prince of Besignano, and Jeanne Eléonore Piccolimini. The latter was a descendant of King Alphonso V of Aragon and his mistress Giraldona Carlino.