[The following note by the Archimandrite Palladius (Eluc. 21-23) throws a great light on the relations between the families of Chinghiz Khan and of Prester John.

“T’ien-te Kiun was bounded on the north by the Yn-shan Mountains, in and beyond which was settled the Sha-t’o Tu-K’iu tribe, i.e.  Tu-K’iu of the sandy desert.  The K’itans, when they conquered the northern borders of China, brought also under their rule the dispersed family of these Tu-K’iu.  With the accession of the Kin, a Wang Ku [Ongot] family made its appearance as the ruling family of those tribes; it issued from those Sha-t’o Tu-K’iu, who once reigned in the north of China as the How T’ang Dynasty (923-936 A.D.).  It split into two branches, the Wang-Ku of the Yn-shan, and the Wang-Ku of the Lin-t’ao (west of Kan-su).  The Kin removed the latter branch to Liao-tung (in Manchuria).  The Yn-shan Wang-Ku guarded the northern borders of China belonging to the Kin, and watched their herds.  When the Kin, as a protection against the inroads of the tribes of the desert, erected a rampart, or new wall, from the boundary of the Tangut Kingdom down to Manchuria, they intrusted the defence of the principal places of the Yn-shan portion of the wall to the Wang-Ku, and transferred there also the Liao-tung Wang-Ku.  At the time Chingiz Khan became powerful, the chief of the Wang-Ku of the Yn-shan was Alahush; and at the head of the Liao-tung Wang-Ku stood Pa-sao-ma-ie-li.  Alahush proved a traitor to the Kin, and passed over to Chinghiz Khan; for this he was murdered by the malcontents of his family, perhaps by Pa-sao-ma-ie-li, who remained true to the Kin.  Later on, Chingiz Khan married one of his daughters to the son of Alahush, by name Po-yao-ho, who, however, had no children by her.  He had three sons by a concubine, the eldest of whom, Kiun-pu-hwa, was married to Kuyuk Khan’s daughter.  Kiun-pu-hwa’s son, Ko-li-ki-sze, had two wives, both of imperial blood.  During a campaign against Haidu, he was made prisoner in 1298, and murdered.  His title and dignities passed over in A.D. 1310 to his son Chuan.  Nothing is known of Alahush’s later descendants; they probably became entirely Chinese, like their relatives of the Liao-tung branch.

“The Wang-Ku princes were thus de jure the sons-in-law of the Mongol Khans, and they had, moreover, the hereditary title of Kao-t’ang princes (Kao-t’ang wang); it is very possible that they had their residence in ancient T’ien-te Kiun (although no mention is made of it in history), just as at present the Tumot princes reside in Kuku-hoton.