He was a successor for ABE no Seimei, and governed the Onmyoryo (Bureau of Divination) as a Tenmondo (ancient horoscopy) Soke (the head family or house), or an Onmyodo (way of Yin and Yang; occult divination system based on the Taoist theory of the five elements) Soke (the head family or house), with his brother, Yoshimasa and another Onmyodo Soke, KAMO no Mitsuyoshi of the Kamo clan.
このように吉平は安倍晴明の後継者であり、また天文道宗家ひいては陰陽道宗家として弟の吉昌、もう一方の陰陽道宗家である賀茂氏の賀茂光栄らと共に陰陽寮を取り仕切っていた。