Complex sentence: Her paternal grandparents were Walter Devereux, 1st Earl of Essex and Lettice Knollys, and her maternal grandparents were Sir Francis Walsingham, Queen Elizabeth's trusted spymaster, and Ursula St. Barbe.
Split into simpler sentences: Her paternal grandparents were Walter Devereux, 1st Earl of Essex and Lettice Knollys. Her maternal grandparents were Sir Francis Walsingham, Queen Elizabeth's trusted spymaster, and Ursula St. Barbe.