The animated version seems to assume that the younger brother (Cao Xuanliang) is Wu Shen and the older brother (Cao) was killed by his younger brother. Since then, the younger brother and brother have been turned upside down, and the younger brother has become a brother. It is the phrase "You will be a brother in the next life". After his brother died, he went into Luo Cha Street and became an undead (that is, what we see now was actually killed by his brother Cao). Later, "Cao Yanbing" (actually Cao Xuanliang, the former brother with Wu Shen's body and the patron saint of Chu Xu) grew up, and "Cao Xuanliang" (actually Cao Yanbing killed by his younger brother) has always been so great to the undead, which is what we see now.

This is just my own understanding. Everyone may have different opinions. Actually, only animation officials can know what it looks like.