Because Imperial Prince Sanehito, who was born to Suemune's older sister, MINAMOTO no Kishi (consort of Emperor Gosanjo), was appointed to be Prince of Emperor Shirakawa, Suemune served as Togu Gon no daibu (Provisional Master of the Crown Prince's Quarters) from 1080 to 1085, when Imperial Prince Sanehito died.
季宗の姉源基子（後三条天皇女御）が産んだ実仁親王(平安時代)が白河天皇の皇太子に立てられたため、季宗は承暦4年（1080年）以後、応徳2年（1085年）に実仁親王が薨去するまでの間、春宮権大夫を務めた。