Serene Highness
His second marriage to Her Serene Highness Princess Florestine of Monaco in 1863 led in part to Wilhelm's elevation in 1867 from being a Count of Wurttemberg to Duke (Herzog) von Urach. He had served the Kingdom well in his career, and the dukedom of 1867 elevated him to his wife's rank of Serene Highness. His new title was similar to the status of a Royal Duke in Britain today.