Majo Maid wa Joou no Himitsu wo Shitteiru.

Liz, who can see the future, has her engagement broken off because of her mysterious power. That sort of woman has been hired as a maid by Her Highness Queen Schriess of Lynphilia. Around Her Highness, who has never married and has no heir, her five younger brothers, the princes, have started a struggle for succession. However, Liz learns that the queen, who must urgently marry for the sake of national peace, has a big secret!?

(Source: Kodansha, translated)