According to "Toungoo Yazawin", Thawun Nge was the more ambitious of the two brothers. He wanted the top job but had to relent as Thawun Gyi became the ruler by primogeniture. Thawun Nge settled for being the deputy. Toungoo became independent in 1287 when its overlord Pagan fell due to the Mongol invasions. Thawun Gyi never submitted to King Kyawswa (r. 1289–97), who ruled only around Pagan, but submitted to the Myinsaing rulers later at an unspecified date.