Complex sentence: Her paternal grandparents were Edmund Mortimer, 3rd Earl of March and Philippa Plantagenet, and her maternal grandparents were Thomas Holland, 2nd Earl of Kent and Lady Alice Fitzalan.
Split into simpler sentences: Her paternal grandparents were Edmund Mortimer, 3rd Earl of March and Philippa Plantagenet. Her maternal grandparents were Thomas Holland, 2nd Earl of Kent and Lady Alice Fitzalan.