I'm looking for the name of an ancient non-transmigration novel. [Key words: adopted son, brother and sister, surname Song, and the woman is retarded.]

I'm looking for the name of a romance novel.
In ancient times, the general content was that this family's surname was Song. Old Master Song had a daughter (female lead) and adopted a son (male lead).
The woman was quite normal at first, but after the whole family died, only she and her unrelated brother were left. Then, I forgot how she became mentally retarded.
After that, the male protagonist occupied the Song family. All the servants hated the female protagonist and didn't even give her food. Then, the male protagonist ignored the female protagonist at first, but later on, he fell in love with the female protagonist for some reason (or maybe he fell in love with her at the beginning but abused her first according to the usual practice).
She forgot about it in the middle, and when it ended, the female lead returned to normal. Then, they got together.

Answer 1

The name of this novel might be " An Foster Son Is Noble." It was an ancient novel about a family surnamed Song who adopted a boy and raised him into an outstanding talent. The heroine in the novel was the adopted daughter of this family, but because of an accident when she was young, she had low intelligence and became a girl with dementia. Between the adopted son and daughter, the family had experienced many twists and turns, but in the end, they successfully cultivated an outstanding talent, allowing the family to obtain greater glory in the imperial court.