Complex sentence: Her paternal gandparents were John II of Armagnac and Jeanne de Périgord, and her maternal grandparents were John, Duke of Berry and Jeanne of Armagnac.
Split into simpler sentences: Her paternal gandparents were John II of Armagnac and Jeanne de Périgord. Her maternal grandparents were John, Duke of Berry and Jeanne of Armagnac.