The paper surveys the distribution of the titles bcan po and khri in historical and non-historical documents of the Tibetan Empire. Their patterns of usage suggest the existence of strict rules that governed the bestowal of the titles within the royal family. In the second part of the paper a new chronology of succession to the throne in the Tibetan imperial dynasty is put forward, based not only on Tibetan imperial documents and post-imperial historiographical works but also on Chinese written sources.