With the two children in the residence, he had more control over his wife as Madam Nan cared greatly for her children. She couldn't bear to see the two of them suffer.
Nan Shu Cheng naturally couldn't mistreat his son.
After all, Nan Luo would be his successor in the future and even if he would not be his successor, he would be more valuable than his daughter. So, he simply punished Nan Hua more, not letting her see his wife.
She's just a daughter.
In his opinion, a woman wouldn't be of much use, but Madam Nan always thought differently.
She loved both of her children.
And they became 'tools' Nan Shu Cheng could use to control his wife. With Nan Hua still staying in his residence, he could make use of her to control his wife.
If Madam Nan wanted to see Nan Hua, she would have to listen to him.