If he had known earlier, he wouldn't be in the situation he is now. That man did say that day, urging Mrs. Jing to quickly find some clues, or else he wouldn't let their family off so easily, because he would have to take action then.
"Xin'er, what are you saying? You're my son, aren't you? How could you not survive? And aren't we a family? How could anything happen?" Jing Xiaonan listened with an increasing sense of dread. When did he learn of these things? Why didn't they know anything, nor saw any signs of it? If Jing Xin intended to do something to them, it would be too terrible.