Complex sentence: In 1541, when Jeanne was thirteen, her uncle King Francis I married her, against her will, to William "the Rich", Duke of Jülich-Cleves-Berg, brother of Anne of Cleves, the fourth wife of Henry VIII of England.
Split into simpler sentences: In 1541, when Jeanne was thirteen, her uncle King Francis I married her, against her will, to William "the Rich", Duke of Jülich-Cleves-Berg. William, Wilhelm, was the brother of Anne of Cleves, the fourth wife of Henry VIII of England.