Complex sentence: Because her brother, who became ruler of the principality of Béarn in 1572 Henry IV of France and Navarre was generally absent in other parts of France, after his escape from captivity in 1576, he entrusted Catherine with the government of Béarn.
Split into simpler sentences: Because her brother, who became ruler of the principality of Béarn in 1572, Henry IV of France and Navarre was generally absent in other parts of France. After his escape from captivity in 1576, he entrusted Catherine with the government of Béarn.