HIKAMI no Kawatsugu was the child of Shioyaki no okimi (Prince Shioyaki or HIKAMI no Shioyaki) and Imperial Princess Fuwa (the Imperial princess of Emperor Shomu) and was also the great-grandchild of Emperor Tenmu, however, Hikami was dethroned due to the execution of Shioyaki no okimi from his involvement in FUJIWARA no Nakamaro's War.
氷上川継は塩焼王（氷上塩焼）と不破内親王（聖武天皇の皇女）の子で天武天皇の曾孫になるが、塩焼王が藤原仲麻呂の乱に与して処刑されたこともあり、皇嗣からは外されていた。