"Margrave Otto V of Brandenburg-Salzwedel (c. 1246 – 1298), nicknamed Otto the Tall, was a son of Margrave Otto III and co-ruler of Brandenburg with his cousin, Margrave Otto IV.
Otto V spent many years in Prague, at the court of his maternal uncle King Ottokar II of Bohemia. When Ottokar died in battle in 1278, Otto V became the regent for Ottokar´s son and heir Wenceslaus II, who was only seven years old when his father died. As regent, Otto V had to deal with the machinations of Ottokar´s widow Kunigunda of Slavonia and with factions of powerful noblemen. Bohemian chroniclers describe Otto´s persistent rigour and that Wenceslaus was forced to give up his claims on Upper Lusatia before he could start reigning himself. When Wenceslaus had taken over, he and Otto V were still on good terms, and Wenceslaus took measures against the strong influence of the group around his mother." - (en.wikipedia.org 06.04.2020)
en