He was born as the fourth son of Hideyoshi SASAKI, who was toryo (head of the clan) of the Sasaki clan, based on Sasaki no sho Manor in Omi Province, and lived in Heian-kyo (the ancient capital of Japan in current Kyoto).
近江国の佐々木庄を地盤とする佐々木氏の棟梁である佐々木秀義の四男として生まれ、平安京に住んでいたとされる。