Complex sentence: He was a minor member of the French royal family but gained prominence when the Capetian main line went extinct, as he and his wife and cousin, Joan II of Navarre, acquired the Iberian kingdom and a number of French fiefs.
Split into simpler sentences: He was a minor member of the French royal family but gained prominence when the main line went extinct. He and his wife, Joan II of Navarre, acquired the Iberian kingdom and a number of French fiefs.