Prince William Victor Charles Augustus Henry Sigismund of Prussia, was the second son of Prince Henry of Prussia and Princess Irene of Hesse and by Rhine. He was the nephew of Kaiser Wilhelm II and Tsarina Alexandra of Russia. As the great-grandson of Queen Victoria through both his parents, he was the only one of three brothers who did not have the hemophilia common among her descendants.

Prince Henry of Prussia was a younger brother of German Emperor Wilhelm II and a Prince of Prussia. Through his mother, he was also a grandson of Queen Victoria. A career naval officer, he held various commands in the Imperial German Navy and eventually rose to the rank of Grand Admiral and Generalinspekteur der Marine.