He was born into the family of Sasaki-Kyogoku clan which served as land stewards in Omi Province, in 1296, and he took over as head of the family after Munetsuna SASAKI, who was his maternal grandfather, in 1304.
永仁4年(1296年)、近江国の地頭である佐々木氏京極氏に生まれ、1304年に外祖父である佐々木宗綱の後を継いで家督を継承する。