Ex - Kaiser ' s favourite grandson killed in action . Prince Wilhelm , oldest son of the former Crown Prince of Germany and favourite grandson of the ex - Kaiser , has been killed in action . In 1933 the Prince morganatically married Fraulein Dorothea von Salviati , sister of a German horseman , in defiance of his family , and renounced his rights to the succession . Photo shows ; Prince Wilhelm of Prussia , wearing the uniform of the Steel Helmet organisation , which was disbanded by the Nazis , with his bride after their wedding in Bonn . 27 May 1933