Complex sentence: He was the oldest son of common land owners, Felicjan and Brygida née Szczakowska, and grew up under the protection of his uncle, Wacław Szczakowski.
Split into simpler sentences: He was the oldest son of the not wealthy land owner Felicjan and Brygida née Szczakowska. He grew up under the protection of his uncle Wacław Szczakowski.