There is a theory that Narihira and Imperial Princess Yasuiko had an affair resulting in the birth of Moronao who was later to be adopted by Shigenori TAKASHINA, resulting in rumors that the Takashina clan were descendants of Narihira.
なお、恬子内親王との間には密通によって高階茂範の養子・師尚が生まれたという説があり、以後高階氏は業平の子孫ではと噂された。