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