Poor Xu Haoran was born not only an omega (which he differentiated into later in life) but also very weak—so weak that his imperial parents were practically already wearing mourning clothes before he was even three hours old! It was as if the whole world was over for them, seeing that their first child was in such a poor state.
It was a miracle that Haoran survived, and as a result, the imperial palace was given the finest gifts and blessings from all the other palaces in the heavenly realm.
As if the empress didn't already have enough stress and worry placed upon her, the realization that her dear son, the first prince, would likely not differentiate into an alpha weighed over her shoulders. If Haoran differentiated into an omega, or even worse a beta, then he would be unable to take the title of crown prince.
Empress Xu loved her son dearly and wished him a lovely future, but she was worried that he would live a life of sorrow solely because off of the gender* he turned out to be. She from then on put in her best effort to give Haoran the best life possible, doting on him quite too much for his liking. Oh, if young Haoran could know the stress he put his mother in...
Until the empress was able to conceive a child suitable for the throne, constant pressure would be placed upon her not only by the imperial palace but the entire heavenly realm. Thankfully, as the second princess Xu Daiyu and eventually the youngest third prince Xu Mingze were born, the palace returned to peace. Relatively, at least.
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Gender*: This is used in reference to the "secondary gender" in omegaverse, which is revealed after reaching the age of 16