Complex sentence: Her paternal grandparents were the 9th Earl of Arundel and Alice de Warenne, and her maternal grandparents were the 3rd Earl of Lancaster and Maud Chaworth.
Split into simpler sentences: Her paternal grandparents were the 9th Earl of Arundel and Alice de Warenne. Her maternal grandparents were the 3rd Earl of Lancaster and Maud Chaworth.