"Wilhelm von Brandenburg (30 June 1498 – 4 February 1563) was the Archbishop of Riga from 1539 to 1561.
A member of the House of Hohenzollern, Wilhelm was the son of Frederick I, Margrave of Brandenburg-Ansbach, the brother of Albert, Duke of Prussia, and the grandson of Albert III Achilles, Elector of Brandenburg and Casimir IV Jagiellon.
After William´s administration as Prince-bishop ended during the Livonian War, Riga became a Free City (1561–1581)." - (en.wikipedia.org 30.01.2020)