Whatever connections you may have I doubt if you are related to Kaiser Wilhelm. In his case his given name was Wilhelm, not his family name which was Hohenzollern. Wilhelm is the German version of William and I think your gt.grandmother's name of Wilhelm would be the equivalent of Williams in English. Try googling Kaiser Wilhelm and you will find all the details of his parents, spouses and children - if you are related you would soon be able to pick up the link.