Kaykhusrev was the son of Kayqubad I and his wife Mahpari Khatun, who was Greek by origin. Although Kaykhusrev was the eldest, the sultan had chosen as heir the younger ‘Izz al-Din, one of his two sons by the Ayyubid princess Adila Khatun, daughter of al Adil I, sultan of Cairo and the Jazira In 1226, Kayqubad assigned the newly annexed Erzincan to Kaykhusrev. With the general Kamyar, the young prince participated in the conquest of Erzurum and later Ahlat. Kaykhusraw himself married Ghazia Khatun, the daughter of the emir of Aleppo, Al-Aziz Muhammad.