He was 3rd son of the Khoshot (Ho shod) chief Ha-nai Noyan (Ha na'i sras). Known as Gu shrī Han Bstan 'dzin chos kyi rgyal po. His given name was Thorol Baihur (Tho rol Ba'i hur). Thuken, p. 126, and especially p. 377.
"In fact, we have no evidence other than the writings of the Fifth Dalai Lama that Guši Qaγan ever gave Tibet to the Dalai Lama." McKeown's dissertation, p. 163.
