This is not unusual with respect to Shigemori, who was Tokuko's foster father, Tokitada, who was Chugu Gon no daibu (provisional master of the Consort's Household), and Koremori, who was Chugu Gon no suke (Provisional Assistant Master of the Consort's Household).
このうち重盛は徳子の養父であり、時忠・維盛はそれぞれ中宮権大夫・権亮なので不思議ではない。