The ancient Tibetan kingdom perished at the death of King Dar ma in 846 A. D. Many Tibetan documents describe his descendants in a stereotyped manner, yet their actual existence has not hitherto been ascertained. However we can vouch for the existence of the descendants with the help of Mkhas pahi dgah ston, Deb gter sṅon po and Tung huang Documents. Further, according to H. E. Richardson's opinion, we can also assess the dates of most of the events in the Central Tibet from the death of Dar ma up to the entry of Atīça into Tibet. After the final assessment of dates, it becomes apparent that the lineage of Yun brtan, the eldest son of Dar ma, had really existed as feudal lords of Bsam yas and that the lineage of Ḥod sruṅ, the second son of Dar ma, had become Yar kluṅs jo bo and occupied exclusively the post of abbot of Spyill bu Temple. The exclusive possession of abbacy was one of the ways of survival by the nobles in the unstable era of Middle Ages. Many other similar cases exist, but a special historical significance may be given to the case of Yar kluṅs jo bo since it took the initiative in such a practice.
