Some Dunhuang documents say that, as well as his sister Sad-mar-kar (or Sa-tha-ma-kar), Songtsen Gampo had a younger brother who was betrayed and died in a fire, sometime after 641. Apparently, according to one partially damaged scroll from Dunhuang, there was hostility between Sa-tha-ma-kar and Songtsen Gampo's younger brother, bTzan-srong, who, as a result, was forced to settle in gNyal (an old district to the southeast of Yarlung and across the Yartö Tra Pass, which bordered on modern Bhutan and Arunachal Pradesh in India). Little, if anything, else is known about this brother.