Tentang
Sibuxiang was a Qilin and the firstborn son of Shi Qilin and Yu Qilin, and later the adoptive brother of Tianlu and Bixie.
He is revealed to have died before the time of the modern-day storyline, at the hands of a member of the Pixiu Clan. This event led to Tianlu's memory wipe, Bixie's disappearance, and the Heavenly Court making Sibuxiang take on the Qilin's identity.
(Source: You Shou Yan Wiki)