Aside from Kenshi/Kiyoko the Emperor had a concubine named FUJIWARA no Seishi (daughter of FUJIWARA no Narutoki) since his days as the Crown Prince, and she had given birth to the First Prince, Prince Atsuakira, and the Emperor decided to make Seishi an Empress.
天皇には妍子とは別に東宮時代からの女御に藤原せい子（藤原済時の娘）がおり第一皇子・敦明親王を生んでおり、天皇は娍子を皇后に立てることとした。