Otto III of Brandenburg

Otto III the Pious (1215–1267), younger son of Margrave Albert II, ruled Brandenburg jointly with his elder brother John I from 1225 until John died in 1266, and then alone for a year. Together they won the Uckermark and carried Ascanian rule beyond the Oder into the Neumark.

In 1255 he joined King Ottokar II of Bohemia on the Prussian Crusade and helped found Königsberg, and in 1256 he was a candidate for King of the Romans.