John of Brienne

(born c. 1170—died March 1237, Constantinople) Count of Brienne (in northeastern France) and later titular king of Jerusalem (1210–25) and Latin emperor of Constantinople (1231–37). The penniless younger son of a French count, he married the queen of the Crusader state of Jerusalem, with the support of Phillip II, and after her death became regent for their infant daughter. He arranged a truce with Egypt (1212) and participated in the unsuccessful Fifth Crusade. In 1228 he became regent and coemperor of Constantinople, and he was crowned emperor three years later. He fended off attacks by Ivan Asen II and John III Ducas Vatatzes.

Source: Encyclopedia Britannica