Eudoxia was the fourth daughter of the Nicaean emperor Theodore II Laskaris and of Elena Asenina of Bulgaria.
[2][better source needed][3] Eudoxia grew up as a princess at the court of Nicaea, where Constance II of Hohenstaufen,[4] widow of her grandfather John III Doukas Vatatzes, also lived.
After the Palaiologan usurpation of the imperial throne, both ladies (dowager empress Constance and Eudokia) fled, travelling the same route from Constantinople to Tende and Sicily, respectively, and years later, both sought protection at the kingdom of Aragon under king James I.
This marriage originated the house Lascaris de Vintimille, which stood until the 19th century as a powerful French family.
Living at Xàtiva and Zaragoza and Castella, she travelled on diplomatic missions for King James II of Aragon.