Peter first married Agnes I, via whom he obtained the three counties of Nevers, Auxerre, and Tonnerre.[3] In 1193 he married secondly to Yolanda,[3] a sister of Baldwin and Henry of Flanders, who were afterwards the first and second emperors of the Latin Empire of Constantinople. Peter accompanied his cousin, King Philip Augustus, on the third Crusade in 1190, returning to France in 1193. He fought (alongside his brother Robert) in the Albigensian Crusade in 1209 and 1211, when he took part in the siege of Lavaur. He was present at the Battle of Bouvines in 1214.
When his brother-in-law, the emperor Henry, died without issue in 1216, Peter was chosen as his successor, and with a small army he left his residence of château de Druyes in France to take possession of his throne. He was consecrated emperor at the Basilica of Saint Lawrence outside the Walls in Rome by Pope Honorius III on 9 April 1217. He then borrowed some ships from the Venetians, promising in return to conquer Durazzo for them, but he failed in this enterprise, and sought to make his way to Constantinople by land.[4] On the journey he was seized by the despot of Epirus, Theodore Komnenos Doukas, and, after an imprisonment of two years, died,[4] probably by foul means. Peter thus never governed his empire, which, however, was ruled for a time by his wife, Yolanda, who had succeeded in reaching Constantinople. Two of his sons, Robert and Baldwin, reigned in turn as emperors of the Latin Empire of Constantinople.
