This essay reviews Confucian ethics with regard to impartiality and Confucian notion of brotherhood. It focuses on the comments by Song Neo- Confucians, Cheng Yi and Zhu Xi, about a famous case involving brotherhood. In this case Diwu Lun of the Han dynasty treated his diseased son and his diseased nephew in different ways. The author argues that Confucianism, starting from a naturalist standpoint, affirms the partiality in the relations between brothers, and judges deliberate impartiality negatively. On this point, one cannot simply view Confucianism as analogous to the Kantian ethics which promises impartiality or the virtue ethics which opposes impartiality.