William was the son of Gerhard VII, Duke of Jülich-Berg and Sophie of Saxe-Lauenburg.

He married the rich Countess Elisabeth of Nassau-Saarbrücken in 1472, but she died in 1479.

Neither marriage produced a son, so the succession of the Duchy became a problem.

William died in 1511, leaving his daughter the final member of the House of Jülich.

John III then became the first ruler of the United Duchies of Jülich-Cleves-Berg, which would exist until 1666.