Emperor Daoguang (r. 1821-1850) had nine sons. The eldest died in 1831, while the second and third died young. In 1832, Yizhu, the later Emperor Xianfeng (r. 1851–1861), was born. In 1833, Yixin, the later Prince Kung was born.
In 1840, the empress died. Emperor Daoguang didn't promote a new empress, so Yixin's biological mother became the person with the highest position as the imperial concubine, to whom Yizhu was entrusted. The two brothers were of similar age and had a very close relationship. They often learned literature and practiced martial arts together.
Although Yizhu and Yixin had no idea of competing for the throne, their teachers secretly began to do so. Zhuo Bingtian, Yixin's teacher, served as the Grand Master for a long time. He was in charge of the Ministry of War, the Ministry of Household and the Ministry of Work. Although Du Shoutian, Yizhu's teacher, had a lower position, he was much better than Zhuo in dealing with affairs and understanding Emperor Daoguang's mind.
According to historical records, two things played an important role in Emperor Daoguang's decision to choose the inheritor.
Emperor Daoguang led his princes to go hunting and took the opportunity to inspect and judge them. The princes were well aware of the importance of this hunting to their political future. Yizhu knew that he was far inferior to Yixin in riding and shooting, so he asked his teacher Du for advice before leaving. Du asked Yizhu not to shoot on the hunt. If the emperor asked, he could say that the spring is the time for birds and animals to live and reproduce, therefore, killing them is not a good thing. Emperor Daoguang asked Yizhu why he killed nothing in the hunt. Yizhu repeated the teacher's instructions. The emperor was very happy and praised him.
Emperor Daoguang was seriously ill and talked with Yizhu and Yixin. They both knew the importance of this conversation and asked their teachers for advice. Zhuo, Yixin's teacher, believed that if the emperor asked, he should tell everything he knew, while Du believed that in terms of knowledge of the current politics, Yixin would certainly be better than Yizhu, so the only way was to cry without talking when the emperor said he was old and seriously ill. Emperor Daoguang was again very pleased, so he made Yizhu the prince imperial.