Wikipedia
Danzhu was the son of the legendary Chinese Emperor Yao (Tang Yao). His mother was a concubine, San Yi.
He was described as vicious and a playboy, and his father Yao is said to have invented the game of Weiqi to favorably influence him. Various stories have him either banished, executed, or attempting (and failing) to kill his father. It was said that "those who had to try a lawsuit did not go to Danzhu, but to Shun."
Sima Qian wrote that "Yao's son Danzhu and Shun's son Shangjun were allowed to have their own territories in order to offer sacrifices to their ancestors", while Qiao Zhou wrote that "Yao's son was given benefice at Tang 唐."
The Bamboo Annals represent Yao as having banished prince Danzhu to Danshui in his 58th year of his reign. They add that following Yao's abdication, Danzhu kept away from Shun, and that after the death of Yao, "Shun tried to yield the throne to him, but in vain." It was at this point that Shun invested Danzhu with Tang. However, an alternative account elsewhere in the Annals holds that Shun dethroned and imprisoned Yao, raising Danzhu to the throne for a short time before seizing it himself.
Despite the fact that Danzhu did not succeed his father in most historical accounts, Danzhu is referred to with the title 帝 (Di, Emperor) in Zhou writings.