The Nāṣirī Generations 75: VIII. 'IZZ-UD-DIN, KAI-KA-US, SON OF KAI-KHUSRAU.

75

According to his father's nomination as successor to the sovereignty, Sultan 'Izz-ud-Din, Kai-Ka-us, ascended the throne of Rum in the beginning of the year 643 H., and the Maliks and other great nobles submitted to his authority.
As he was celebrated for his energy, his warlike accomplishments, and his nobility of mind, he strengthened his frontiers on the side of Afranj; and, as a matter of necessity, consequent upon the power and predominance of the infidel Mughals over the dominions of Islam, he, in order to ward off [the inroads of] that race, despatched his younger brother into Turkistan to the Court of Mangu Khan, the Mughal, so that he might, under terms of peace, be left in possession of his dominions.
On Rukn-ud-Din, Kulij-Arsalan, the envoy and brother of Sultan Kai-Ka-us, reaching the presence of Mangu Khan, the Mughal, he preferred requests, and made solicitations contrary to the mandate of his brother. He sought from Mangu Khan the territory of Rum for himself, and likewise assistance from him to enable him to liberate that country from the hands of his brother. Mangu Khan gave him the daughter of the Nu-in [a Prince, or a great noble,] Aljakta, the Mughal, and despatched Aljakta, with his troops, to aid Rukn-ud-Din, Kulij-Arsalan [against his brother]. When they reached the Rumi territory, ’Izz-ud-Din, Kai-Ka-us, retired before them; and Kulij-Arsalan and the Mughals became dominant over Rum. Kai-Ka-us went to Aor Khan of Rum, and, having obtained aid from him, came and suddenly attacked the Mughals and overthrew them. He captured his brother, and immured him in a fortress.
After some time, he, Kulij-Arsalan, succeeded in escaping, and went to the Mughals; and, as what has happened since has not become known to the author, this [notice of him] has been thus much abridged.