Complex sentence: Charlotte's paternal grandparents were James I, Count of La Marche and Jeanne de Châtillon, and her maternal grandparents were Jean VI, Count of Vendôme and Jeanne of Ponthieu.
Split into simpler sentences: Charlotte's paternal grandparents were James I, Count of La Marche and Jeanne de Châtillon. Her maternal grandparents were Jean VI, Count of Vendôme and Jeanne of Ponthieu.