In the later period of the reign of the Kangxi Emperor of the Qing Dynasty, a fierce struggle broke out over the position of crown prince, which was called "nine sons and concubines" by posterity. As the name suggests, in the process of this struggle for the throne, nine princes were directly involved in it, they were the emperor's eldest son Yin Zhen, the emperor's second son Yin Rong, the emperor's third son Yin Zhen, the emperor's fourth son Yin Chen, the emperor's eighth son Yin Yu, the emperor's ninth son Yin Yu, the emperor's tenth son Yin Yu, the emperor's thirteenth son Yin Xiang, and the emperor's fourteenth son Yin Yu. So, what is the end of these people?

1. Death by imprisonment and persecution
Among the nine princes, the first to die was the second son of the emperor, Yin Rong, who was imprisoned by the Kangxi Emperor after the two were deposed, and died in the place of imprisonment in December of the second year of Yongzheng at the age of 51. The second to die was the ninth son of the emperor, Yin Yu, who supported the Eight Brothers in the competition for the throne, so after the Yongzheng Emperor ascended the throne, he was persecuted. In the fourth year of Yongzheng, Yin Yu was stripped of his clan and renamed "Seth Hei", and was persecuted during his imprisonment in Baoding, "locked in iron, detained by his hands and siblings", and his last life was whimpered.
Shortly after Yin Yu's death, The Eighth Son of the Emperor Yin Yu (renamed "Akina"), who was imprisoned in Beijing, also came to the end of his life, and he vomited in the prison and fell ill and died, according to which some people speculate that he may have died of poisoning. Personally, I think that Yin Yu's death should be similar to Yin Yu's death. Also persecuted and killed by the Yongzheng Emperor was the third son of the emperor, Yin Zhi, who was stripped of his title in the eighth year of Yongzheng and imprisoned in Jingshan, where he died in the forbidden place in the tenth year of Yongzheng. In the twelfth year of Yongzheng, the eldest son of the emperor, Yin Zhen, who had been imprisoned for more than thirty years, also died.
2. Dan Yao poisoned to death
In the struggle of the "Nine Sons and Concubines", the fourth son of the Emperor, Yin Chan, won the victory and began his rule, but his rule did not last for many years. In the end, the Yongzheng Emperor actually killed himself! In August of the thirteenth year of Yongzheng, the Yongzheng Emperor died violently in the Yuanmingyuan. Although the official record seems to be a good death, according to the notes of Qing officials, it can be seen that the Yongzheng Emperor died very suddenly. The day after the death of the Yongzheng Emperor, the Qianlong Emperor issued an edict, which was quite a meaning of wanting to cover up the mizhang.
The Qianlong Emperor said, "The Emperor has been studying for ten thousand years, and he has heard that there is a saying of fire cultivation outside. The Sacred Heart knows its wrongs and wants to try its tricks, thinking that the game is the tool of elimination. Because Zhang Taixu, Wang Dingqian, and several others were placed in the vacant land of Xiyuan. The Sacred Heart regards it as a haiyou person, and has never listened to his words, has not used a medicine, and knows that he is a rogue in the city, and it is best to make trouble. The Emperor's examination has repeatedly spoken to the Emperor and the Prince. However, it turned out that the Yongzheng Emperor not only personally refined Dan, but also took Dan medicine, resulting in his violent death.
Third, the luck was able to die well
Among the three people who died well, the thirteenth son of the emperor, Yin Xiang, had the best ending, because he was a close confidant of the Yongzheng Emperor, so he was reused after the Yongzheng Emperor ascended the throne, and was not only named the Prince of Yi, but also became the King of iron hats. However, Yin Xiang's life expectancy was not long, and he died of illness in May of the eighth year of Yongzheng at the age of 45. The other two princes were able to die well only because they survived the Yongzheng Emperor and met their fairly good nephew, the Qianlong Emperor.
In the second year of Qianlong, the Qianlong Emperor decreed that his two uncles be pardoned, one was the Tenth Brother Yinyu and the other was the Fourteenth Brother Yinyu, and the two not only regained their freedom, but also were awarded the title of Duke of Fuguo. Four years later, Yin Died of Illness, and the Qianlong Emperor ordered that he be buried with a shell grade. Yin Yu lived a little longer, so he was constantly promoted, and was successively named The Prince of Baylor and the King of Gong County, and also held the position of the commander of the Han Army under the Yellow Banner. Twenty years after Qianlong, as the last of the "Nine Sons and Sisters", Yin Yu fell ill and died at the age of 68.
References: 1. Qing Shilu, 2. Research on the Yongzheng Emperor and His Secret Folding System