When he regained consciousness, the warning mistake had already been made.
Soon after, his elder sister-in-law became pregnant. To keep it from his elder brother, they drugged him, insisting that they needed to produce an heir for him.
His elder brother believed them.
Consequently, he genuinely thought that the child his sister-in-law was carrying was his.
Throughout her pregnancy, his elder sister-in-law expressed her regret more than once, even considering aborting the child. Even after the child was born, she was extremely indifferent towards it.
Only over time, as Mingming began to laugh, and call for his mother, did her stern heart begin to soften.
Remembering past mistakes, he was perennially worried that his sister-in-law would not want to see the child, truly viewing him as an illegitimate child. So, he took Mingming to his own courtyard.
... When did his elder brother find out?