According to "Heike Monogatari," Gion no nyogo, who was in Cloistered Emperor Shirakawa's favor and was impregnated by him, was granted to Tadamori, and Kiyomori was born; however, this story has low credibility, since "Heike Monogatari" was completed after the Kamakura Era and it was estimated that Gion no nyogo at that time was over 40 years old.
『平家物語』では白河法皇の寵愛を受けて懐妊した祇園女御が、忠盛に下賜されて清盛が生まれたとなっているが、『平家物語』の成立は鎌倉時代以降であり、祇園女御は当時40歳を越えていたと推測されることから信憑性は薄い。