Both have a similar plot of the FL marrying the prince who then becomes the emperor. Both FLs become trapped between the two royal brothers as well as the emperor's evil concubines. Both FLs lose at least one child due to the emperor, and are believed to have lost their fertility as well (in the movie BCTSAL the FL learns she is pregnant again). A lot of both dramas are set within a palace and the FL undergoes a lot of hardship and emotional growth.
Both are historical dramas in which the ML is ill with a short time left to live that he then shortens saving the FL. They are weak physically but strong mentally and in both dramas are involved in the power struggle for the throne. Both MLs are doctors or work as doctors for a time. Both FLs misunderstand and are separated from the ML for a long time.
Very similar love story... but Yun Xi has a better ending.. in my opinion.. yun xi is a girl with unique talents but she ends up figuring out that her father isnt her real father .. and her actual father is the man that poisoned her husband ... theres a lot more to it .. but you'll just have to watch this masterpiece to find out ... it is based off of a novel