Mutual first loves, 1v1 HE, short story, pseudo-incest.
This is not a female-dominated society. In this setting, either princes or princesses can become emperor.
Prince An and the empress grew up together. He was her most trusted confidant, and everyone at court knew it. After his effective work on disaster relief, he became the only minister permitted to carry a sword into court. When he rebelled, the ministers were shocked, but the empress was delighted.
In Prince An's residence, they found portraits of the empress that he had painted over the years.
She was very pleased.
So she wasn't the only one in love after all?
Theme: People should trust one another