Responses
I think its probably an age thing. Its normal for men as they get older, to become less likely to fertilize a woman's egg. Just as it becomes harder for a woman to becomes pregnant and stop producing eggs. Theres nothing strange about it. He's an old man, so its accepted as such. Especially if his doctor thoroughly examined him, then his Dr would've told him its normal for his age
So the emperor just accepted that he was infertile and didn't even question the birth of his previous children? Didn't wonder how he became infertile? In those times women were punished quite harshly even if there wasn't any proof. So for him to just accept that he only recently became infertile and all the previous kids are his is so absurd. He should have questioned the empress about his previous kids birth as well or at the very least, the author should have given some sort of other explanation