Qi Xiuyuan was filled with hatred, so he refused to leave the Qi Residence no matter what. He had always had a faint doubt in his heart. If he hadn't leaned against the window and instead run into the house at that time, would Madam Wu and his father not have said those words to hurt his mother? Perhaps his mother wouldn't have died from anger then.
Moreover, because of his mother's death, Qi Haoran was accused of jinxing his mother. The little Qi Xiuyuan felt guilty towards his mother and younger brother. Also, he felt much better watching his enemy suffer.
Although Qi Feng didn't like Qi Xiuyuan, he was his flesh and blood after all. Hence, even though Qi Xiuyuan hated him, the two sides had always maintained a balance.
However, this balance was quickly broken because the two uncles of the Zhu family soon learned the truth about their sister's death from Xia Tong.