Complex sentence: Her father was created Earl of Essex in 1572, and her brother, Robert Devereux, Viscount Hereford, inherited the Earldom of Essex on their father's death in 1576.
Split into simpler sentences: Her father was created Earl of Essex in 1572. Penelope's brother, Robert, Viscount Hereford, inherited the Earldom of Essex on their father's death in 1576.