Complex sentence: Her paternal grandparents were Baudoin des Roches and Alix de Châtellerault, and her maternal grandparents were Robert de Sablé and Clémence de Mayenne, daughter of Geoffroy, Sire de Mayenne and Isabelle de Meulan.
Split into simpler sentences: Her paternal grandparents were Baudoin des Roches and Alix de Châtellerault. Her maternal grandparents were Robert de Sablé and Clémence de Mayenne, daughter of Geoffroy, Sire de Mayenne and Isabelle de Meulan.