• Born: Between 1170 and 1175, Acre, Palestine
• Married (1): 14 Sep 1210, Tyre
• Married (2): 23 Apr 1214
• Married (3): 1224, Toledo, Castile
• Died: 27 Mar 1237, Constantinople, Byzantium

  Research Notes:

"Johan de Briene" is named as brother of Gauthier de Brienne by William of Tyre (Continuator), after his brother Guillaume. "Gualterius comes Brene" donated property to Beaulieu (Aube) by charter dated 1194 with the consent of "Willelmi et Johannis fratrum eius". The Chronicle of Alberic de Trois-Fontaines names "Iohannis frater eiusdem comitis Galteri comitis Briennensis" when recording that he succeeded as Comte de Brienne after the death of his brother. "Johannes comes Brene" donated property to Basse-Fontaine by charter dated Apr 1210. His first marriage was arranged by Philippe II King of France, who gave him a dower of 40,000 silver pounds, a sum which was equalled by Pope Innocent III.

He landed at Acre 13 Sep 1210, was married to his first wife the next day, and was crowned 3 Oct 1210 at Tyre as JEAN King of Jerusalem by Albert Patriarch of Jerusalem. "Iohannes…Latinorum Ierusalem rex decimus et comes Brena et domina Maria uxor mea regina" donated property to the church of the Holy Sepulchre, Jerusalem by charter dated 1 Jul 1211. He retained the bailiship of the kingdom of Jerusalem after the death of his first wife, nominally in the name of his daughter. After a long siege, and with the help of western armies which were part of the Fifth Crusade, Damietta in Egypt was captured 5 Nov 1219 and added to the territory of the kingdom of Jerusalem. Jean left the crusade in Feb 1220, intending to visit Armenia to claim the throne in the name of his second wife following the death of her father, but as both she and their infant son died before he sailed for Cilicia he had no further claim and abandoned the journey. He arrived back with the Fifth Crusade 6 Jul 1221, which proceeded to march further into Egypt but was forced to retreat and return Damietta 8 Sep 1221. After appointing Eudes de Montbéliard as regent, King Jean sailed from Acre in autumn 1222, to find a suitable husband for his daughter. He agreed to her marriage with Friedrich II King of Germany on condition that he continued as regent of Jerusalem for life. Matthew Paris records that “Johannes de Brennes rex Jerusalem et magister superioris Hospitalis fratrum Jerusalem” visited England “circa octavas Apostolorum Petri et Pauli” to seek help for the relief of “Terræ Sanctæ”. His son-in-law reneged on his promise relating to the throne of Jerusalem immediately after his wedding and declared himself king of Jerusalem in 1225.

He was appointed regent of the Latin empire of Constantinople, by agreement at Perugia in Apr 1229, and was crowned JEAN Emperor of Constantinople on his arrival in the city in 1231.

The Chronicle of Alberic de Trois-Fontaines records the death in 1237 in Constantinople of "rex Iohannes". ²