Complex sentence: Her paternal grandparents were Geoffrey V, Viscount de Chateaudun and Alix de Freteval, and her maternal grandparents were William des Roches, Seneschal of Anjou, and Marguerite de Sablé, daughter of Robert de Sablé and Clémence de Mayenne.
Split into simpler sentences: Her paternal grandparents were Geoffrey V, Viscount de Chateaudun and Alix de Freteval. Her maternal grandparents were William des Roches, Seneschal of Anjou, and Marguerite de Sablé, daughter of Robert de Sablé and Clémence de Mayenne.