Complex sentence: Her paternal grandparents were John Marshal and Sybil of Salisbury, and her maternal grandparents were Richard de Clare, 2nd Earl of Pembroke, known as "Strongbow", and Aoife of Leinster.
Split into simpler sentences: Her paternal grandparents were John Marshal and Sybil of Salisbury. Her maternal grandparents were Richard de Clare, 2nd Earl of Pembroke, known as "Strongbow", and Aoife of Leinster.