Please recommend a book with the main theme of the female protagonist traveling back to the Kangxi era and becoming the empress.

Please help me find this book. First of all, the female protagonist traveled back to the Kangxi era and became the empress of Kangxi. Because she said that she would only be the empress, Kangxi let her be the empress. Then, the female protagonist's age was actually about the same age as the emperor's princes. Fourth Brother also liked the female protagonist. The female protagonist was good friends with the princes. Then, Fourth Brother married a woman who looked very much like the female protagonist. However, after that woman gave birth to Fourth Brother's child, she became a vegetable. Then, Kangxi died, but he actually didn't die. He had found someone to cast a spell to bring him to the modern world, and he had even promised the female protagonist that he would be with her again in the modern world. After Kang Xi died, the female protagonist was so sad that she transmigrated into the body of the woman who looked like the female protagonist, and then she got together with Fourth Brother. In the end, they lived for quite a long time before they returned to the modern world. Then, Kangxi found the female protagonist and got back together with her. Fourth Brother and the other brothers were also in the modern world ~