Complex sentence: Yolande's paternal grandparents were Robert II, Count of Dreux and Yolande de Coucy, and her maternal grandparents were Guy de Thouars and Constance, Duchess of Brittany.
Split into simpler sentences: Yolande's paternal grandparents were Robert II, Count of Dreux and Yolande de Coucy. Her maternal grandparents were Guy de Thouars and Constance, Duchess of Brittany.