I recommend "Reborn as a Concubine". The main character of the novel is called Xin 'er. She is an empress who was neglected by her husband. However, after her rebirth, she began her journey of fighting in the palace. She had an older brother called Xin Yun, and in the story, there was also a beloved concubine. I hope you like this fairy's recommendation. Muah ~😗