Prince Friedrich Karl Nikolaus of Prussia was the son of Prince Charles of Prussia (1801–1883) and his wife, Princess Marie of Saxe-Weimar-Eisenach (1808–1877). Prince Friedrich Karl was a grandson of King Frederick William III of Prussia and a nephew of Frederick William IV and William I.

Prince Frederick Charles Alexander of Prussia was a younger son of Frederick William III of Prussia. He served as a Prussian general for much of his adult life and became the first Herrenmeister of the Order of Saint John after its restoration as a chivalric order. Nevertheless, he is perhaps remembered more often for his patronage of art and for his sizable collections of art and armor.