After the abolition of the German throne in 1918, the heads of the House of Hohenzollern have claimed to be the titular Kings of Prussia and German Emperors. These claims cannot be separated because according to the Constitution of the German Empire, whoever was King of Prussia was also German Emperor. But since the (2nd) German Empire was abolished this claim does not hold now even if a new German Empire was to formed.
Hohenzollern Pretenders to the Prussian and German throne