The crown prince was not necessarily the eldest son. In ancient times, the crown prince was usually the emperor's eldest son, the eldest son born by the empress. However, there were some exceptions. For example, in the three emperors of Kangxi, Yongzheng, and Qianlong, their eldest sons were not the eldest sons of the legitimate family, but the eldest sons of the concubines. Kang Xi's eldest son, Yin Bi, missed the opportunity to become the crown prince because his biological mother was only a concubine and not his wife. Therefore, it could be concluded that the crown prince was not necessarily the eldest son.

The eldest son was not necessarily the crown prince. The crown prince was the first heir to the throne in feudal society, and was usually the eldest son of the emperor. However, the eldest sons of the Kangxi, Yongzheng, and Qianlong emperors were not the eldest sons of the Di, but the eldest sons of the Shu. Kangxi's eldest son, Yin, lost the position of crown prince because his mother was only a concubine and not his wife. Kangxi conferred the title of crown prince on his second son. Similarly, the eldest son of Yongzheng and Qianlong could not become the crown prince because of the difference in birth status. Therefore, although these eldest sons had stayed by the emperor's side for the longest time, they were not qualified to inherit the throne, nor were they called crown princes. Therefore, it could be concluded that the eldest son was not necessarily the crown prince.
In Joy of Life, the eldest princess and the crown prince did not have a son.
The difference between the eldest son and the crown prince was their status and inheritance. The crown prince was the first heir of the emperor in feudal society. Only the legal heir (the eldest son of the emperor) could be called the crown prince or crown prince. The eldest son was the first son of the emperor. He might not inherit the throne, but it depended on the situation. Therefore, the crown prince was designated as the successor of the next generation and had the responsibility and status to inherit the throne, while the eldest son might not necessarily inherit the throne.
The difference between the eldest son and the crown prince was their status and inheritance. The crown prince was the first heir of the emperor in feudal society. Only the legal heir (the eldest son of the emperor) could be called the crown prince or crown prince. The eldest son was the first son of the emperor. He might not inherit the throne, but it depended on the situation. Therefore, the crown prince was the chosen heir to the throne and had a higher status, while the eldest son was only the son of the emperor and had a lower status.
There were a few reasons why the eldest son of Kangxi, Yin, was not made the crown prince. First of all, his mother was not the empress, but a concubine. In the tradition of choosing a crown prince, the son of the empress was usually the first. Secondly, the eldest son of Emperor Kangxi was not Yin Bi, but Cheng Hu, but he died young. According to his status, Yin He could not be made the crown prince. In addition, Yin's mother was Emperor Kangxi's wife, but she died shortly after Yin's birth. Emperor Kangxi missed her very much, so he made Yin Ni the crown prince shortly after he was born.
In " Joy of Life," the plot where the Eldest Princess sacrificed herself to the Crown Prince was not clearly stated. According to the information on the Internet, some articles mentioned that the Eldest Princess sacrificed herself to the Crown Prince in episode 22, while others mentioned that it was in episode 15. It should be noted that this information may come from different versions of the series or different interpretation of the content of the series. If you want to know the specific content of the series, I suggest you watch the series or look for more detailed information.
In the original novel of Joy of Life, there was a special relationship between the Eldest Princess and the Crown Prince. The Crown Prince persuaded the Eldest Princess to sacrifice herself in exchange for the peace of the Crown Prince's family and prevent the outbreak of war. However, their affair was eventually exposed by Fan Xian. After the Qing Emperor learned of it, he was very angry. He put the Eldest Princess under house arrest and prepared to depose the Crown Prince. After the Eldest Princess learned of the Qing Emperor's plan, she secretly joined forces with the Qin family and the Ye family to kill the Qing Emperor and push the Crown Prince to the throne. However, the Eldest Princess 'plan was leaked by a spy from the Ye family. In the end, the Eldest Princess and Crown Prince chose to commit suicide. In general, the relationship between the Crown Prince and the Eldest Princess played an important role in the story, showing the struggle and choice between power and love. The search results did not provide any clear information on how the Qing Emperor had found out about their affair.
The plot of the Eldest Princess and the Crown Prince appeared in the 15th episode of the TV series Joy of Life.
The Crown Prince and Princess Royal were two important characters in Joy of Life2. According to the description in the first document, there was conflict and conflict between the Crown Prince and Eldest Princess and Fan Xian. The Crown Prince was personally involved in the struggle, and the Eldest Princess secretly supported the Crown Prince and was unwilling to let Fan Xian take over the palace treasury. They tried to test, probe, and even plot against Fan Xian. The existence of the Crown Prince and Eldest Princess placed Fan Xian in danger and the unknown. He needed to protect himself and the people around him and fight for the peace and prosperity of the Qing Kingdom. The conflict between them made the plot even more intense and eye-catching.
In ancient times, the eldest princess was usually the emperor's sister, and the crown prince was the emperor's son, usually the emperor's eldest son. Thus, the Eldest Princess and the Crown Prince were siblings. In web novels, the relationship between the Eldest Princess and the Crown Prince might be different. The specific situation depended on the setting and plot development of the novel.