Hasar, as a child, was thrown out of the Borjigin tribe along with the rest of the family by the Taichiud warlord Targhutai Hiriltug.
[3] Hasar and his brother Temüjin, who later became known as Genghis Khan, killed their half-brother Behter as he returned from a fresh hunt.
Temüjin then gathered new adherents among the Mongols, tricked his rival Ong Khan with a fake message of surrender from his missing brother Hasar, and crushed the Keraites in late 1203.
The princely houses of Hasar, Hachiun, and Temüge tended to coordinate with the five powerful clans: the Jalayir, Khunggirad, Ikires, Uruud, and Mangghud.
Although Shigdür joined the rebellion against Khubilai led by Temüge's great-great-grandson Nayan, the princely house survived without confusion.
Sources show that Qasarid princes continued to hold the title even after the Yuan dynasty collapsed.
It is also claimed that one Qasarid prince was killed in order to protect the last Great Khan Toghogan-Temur from Ming troops.
[5] It is widely accepted that Hasar's descendant Bolunai was a historical figure since his existence is confirmed in contemporary Chinese sources of 1463, 1467, and 1470.
The Dorbeds in Heilongjiang submitted to the Qing in 1624, and they were organized into a banner in Jirim league ruled by descendants of Hasar.