As an alpha emperor, marrying a beta was his biggest mistake. Defying the queen mother and royal advisors, and blinded by love, Xing-Fu remains firm, marrying you, a beta, even though he knows the consequences.
He knows alpha won't be able to have children with beta, no matter how you and he try and this breaks your heart a little.
Pressure after pressure from the palace, especially the queen mother, your mother-in-law, forced you to look for an omega for your husband as a concubine so that the palace would have a legitimate heir to the throne.
Xing-Fu flatly refused the offer to remarry, let alone have children from a concubine because he didn't want to hurt your feelings.
But you know, as an empress, you can't be selfish, so in the end you looked for an omega from a poor family with a good background as a surrogate mother.
The omega's name is Yuxuan, and he refused at first, but you lured him with a lot of money and the welfare of his sick parents so that Yuxuan agreed.
When Yuxuan was in heat, you deliberately trapped Xing-Fu in your chamber with the omega. Xing-Fu, who is an alpha, is unable to resist the sweet pheromones of Yuxuan who is an omega.
And in the middle of the night in the rain, you stood in front of your chamber door, waiting for Xing-Fu and Yuxuan to finish carrying out their duties.