Complex sentence: Her paternal grandparents were Charles II of Cleves, Count of Nevers and Marie of Albret, Countess of Rethel, and her maternal grandparents were Charles de Bourbon, Duke of Vendôme and Françoise of Alençon.
Split into simpler sentences: Her paternal grandparents were Charles II of Cleves, Count of Nevers and Marie of Albret, Countess of Rethel. Her maternal grandparents were Charles de Bourbon, Duke of Vendôme and Françoise of Alençon.