This means that the Regent, FUJIWARA no Yorimichi, was Asatada's great-grandson and Emperors Goichijo and Gosuzaku were his great-great grandsons (grandsons of his grandson).
つまり、関白藤原頼通は朝忠の曾孫、後一条天皇・後朱雀天皇の両天皇は朝忠の玄孫（孫の孫）にあたることになる。