It is written in "Kofuku-ji Engi (Origin of Kofuku-ji Temple)" that there are certain matters about Fuhito's birth that haven't been officially recorded; meanwhile, it is explicitly stated in Okagami, Kugyo Bunin (Official Records of the Ancient Government) and Sonpi Bunmyaku (Ancient Family Tree Charts) that Fuhito was Emperor Tenchi's child born out of wedlock.
なお、『興福寺縁起』には不比等の出生につき「公避くる所の事有り」とあり、大鏡、公卿補任、尊卑分脈には明記され、天智天皇の御落胤であるとする。