Narihira was a direct-line descendent of the Imperial Family, but entered civillian life and took the clan name of Ariwara with his older brother, ARIWARA no Yukihira, after his grandfather and father had been defeated in power struggles.
家系からすれば天皇家の嫡流でもあったが、祖父と父が権力闘争に敗れたこともあり臣籍降下して兄在原行平らとともに在原氏を名乗る。