Complex sentence: Andrzej Gryfita was a descendant of Bogislaw XIV, Duke of Pomerania and his brother, Clement of Brzeźnica both were the member of the noble Gryf family.
Split into simpler sentences: Andrzej Gryfita was a descendant of Bogislaw XIV, Duke of Pomerania. Andrzej and his brother, Clement of Brzeźnica, were both members of the noble Gryf family.