Wu Zhangkong Beloved: Long Bing.
It was after Tang Wulin came to the world and the protagonist left Dragon Tomb. During that time, Long Bing was killed by his father Dark Hummingbird.
It is mentioned in the original work that Wu Zhangkong returned to Shrek Inner Court after thirteen years and knelt down to give Tang Wulin a chance to take the entrance exam.
Less than half a year ago, Tang Wulin and Xie Xie went to the Tang Sect to receive contribution points, which showed that Tang Wulin was thirteen years old, five months and six days old. (Xie Xie was one month and five days younger than him)
Dragon Emperor/Long Zijin and Tang Wulin are the same age but a month younger, because time in the Divine Realm flows at a different speed than time in the mortal world, and the protagonist is Tang Wulin brought Golden Dragon King Bloodline+Divine Core to land and Douluo was reincarnated, and Tang Wulin was born long before Golden Dragon King was hacked to death.
So in summary, Tang Wulin and Long Zijin were born about three or four months after Long Bing died.
Now is the ninth anniversary of Long Bing.
This will support the next plot.