Complex sentence: Henry was 21 when he, his father and brothers captured the Moorish port of Ceuta in northern Morocco, that had long been a base for Barbary pirates who raided the Portuguese coast, depopulating villages by capturing their inhabitants to be sold in the African slave market.
Split into simpler sentences: Henry was 21 when he and his father and brothers captured the Moorish port of Ceuta in northern Morocco. Ceuta had long been a base for Barbary pirates who raided the Portuguese coast, depopulating villages by capturing their inhabitants to be sold in the African slave market.