Why did Ding Youkang kill Ding Youjian's son?

Ding Youkang didn't kill Ding Youjian's son.

According to Youku's video query, Ding Youkang didn't kill Ding Youjian's son in the TV series Unfortunate. Ding Youkang is Ding Youjian's younger brother. He had some plots against Jie Jun, which did not directly lead to his death. Ni, who was lost as a child, reunited with Ding Youkang, but did not know Ding Youkang's true identity. Ding Youkang planned a series of plots in order to inherit the property of the Ni family.