Prince Friedrich Wilhelm of Prussia was a member of the House of Hohenzollern, great-grandson of King Frederick William III of Prussia.
Friedrich Wilhelm and his wife Agatha, 1910
Princess Marie of Saxe-Altenburg was the wife of Prince Albert of Prussia, Regent for the duchy of Brunswick.
Prince Friedrich Wilhelm of Prussia
…Poland) youngest child of Prince Albert of Prussia (1837–1906), (son of Prince Albert of Prussia and Princess Marianne of the Netherlands) and his wife, Princess Marie of Saxe-Altenburg (1854–1898), (daughter of Ernst I, Duke of Saxe-Altenburg and Princess Agnes of Anhalt-Dessau). He was a great-grandson of King Frederick William III…
Princess Marie in 1877