John III Doukas Vatatzes
Robert of Courtenay had been crowned emperor on 25 March 1221. According to George Acropolites he was betrothed to Eudokia Laskarina in 1221. She was a daughter of Theodore I Laskaris and Anna Komnene Angelina. Eudokia was also a younger sister to both Irene Lascarina, wife of John III Doukas Vatatzes and Maria Laskarina, wife of Béla IV of Hungary. However the marriage was opposed by Patriarch Manuel I of Constantinople on grounds of consanguinity. Though not actually closely related by blood, Eudokia was a stepdaughter of Marie de Courtenay who was third wife of Theodore I and sister to Robert. Eudokia was already present in Constantinople. She had been taken there by her paternal uncles Alexios and Isaac Laskaris who had left the Empire of Nicaea following the death of Theodore I. Both uncles joined the military service of the Latin Empire. According to Acropolites, they co-led a Latin force into Bithynia during 1224. They were defeated by their kinsman John III Doukas Vatatzes, captured and blinded.