Polish nobility): just five Polish families, including the Radziwiłłs, received the title of imperial prince from the Holy Roman emperor. Religion The Radziwiłł family also divided on religious grounds. Following the Protestant and Polish Reformation, two branches converted to Calvinism. One branch, the Nesvizh–Kletsk-Olyka line, remained as Calvinists for two generations until the children of Mikołaj "the Black" converted to Roman Catholicism before the end of the century. The Biržai-Dubingiai line remained in the Protestant faith until the extinction of their line one century later. Both Mikołaj "the Black" and Mikołaj "the Brown" were zealous promoters and active participants of the Protestant religion within the GDL. Mikołaj "the Black" funded the printing of a second version, and first completed, Polish translation of a Protestant Bible, titled the "Radziwiłł Bible" (also known as "Biblia Brzeska"), which was published in the town of Brest in 1564. His death in 1565 was seen as a severe loss to the Protestant cause in Lithuania. However, Mikołaj "the Red" continued his cousin's work by founding and endowing land to several churches and schools. Politics Several prominent family members have been involved in domestic and foreign political arenas. They took an active part in the political life of the Grand Duchy of Lithuania. Its importance is manifested by family relations with such famous nobility dynasties in Belarus, Ukraine, Poland, the Great Duchy of Lithuania, Samogitia, and Rus like Zaslawski, Rohatinski, Lukomski, and Olshanski-Dobrowicki. The Radziwiłł family joined the rest of the nobility as the state's elite after the signing of the Union of Krewo in 1385. The significance of the Radziwiłł family is proved by the marriage of Anna to Konrad III Rudy, duke of Masovia, who owned the largest Polish principality. In 1547 Barbara Radziwiłł was married to Sigismund II Augustus, thus becoming the Queen of Poland and setting also in motion a closer relationship to the Papal Curia. Later the Radziwiłłs established family relations not only with the most important families of the Polish, Belarusian and Lithuanian magnate families like Sanguszko, Sapieha or Chodkiewicz, but also with members of royal families like Wiśniowiecki, Sobieski, and Leszczyński. The political position of the Radziwiłłs was enhanced in the 16th century. In 1515, Mikołaj, as a member of a delegation, headed by King Sigismund I the Old took part in the First Congress of Vienna in Pressburg and Vienna where Emperor Maximilian I met kings of Poland,