Complex sentence: He was the son of Andrés Hurtado de Mendoza, 2nd Marquis of Cañete--and viceroy of Peru--and Maria Manrique, Countess of Osorno daughter of the Count of Osorno, belonging to one of the most important families in Spanish aristocracy.
Split into simpler sentences: He was the son of Andrés Hurtado de Mendoza, 2nd Marquis of Cañete--also a viceroy of Peru--and María Manrique, Countess of Osorno. As the daughter of the Count of Osorno, his mother belonged to one of the most important families in the Spanish aristocracy.