The Qing Dynasty did not choose the crown prince without distinction between concubines, but more importantly, there was no concubine to choose from. The empress dowager of Shunzhi had no sons, and although the concubine born to the empress of Kangxi was made crown prince, she was deposed without controversy, and the concubine born to Empress Yongzheng died early; Qianlong very much wanted to set up a concubine, but unfortunately the two concubines born to the empress died early; Jiaqing was very lucky to finally be able to establish the de facto eldest son of the concubine to succeed to the throne; Daoguang also chose the de facto eldest son born of the whole empress to succeed to the throne; Xianfeng had no concubine, only one concubine, and had no chance. To sum up, after entering the customs, the Emperor of the Qing Dynasty wanted to set up a concubine, but most of them did not have the opportunity.
Zhu Changluo died only a month later than his father, Emperor Wanli. If the Wanli Emperor had persisted for more than a month, there would have been no Zhu Changluo, Zhu Youxiao, and Zhu Youjian. Zhu Changyuan would not have been killed like a pig by Li Zicheng's peasant army and drunk Fulu wine later. Following the principle of having a concubine and not having a concubine, establishing an heir as soon as possible is conducive to the stability of the dynasty, but it also has a fatal flaw, this kind of non-selective inheritance method regardless of merit and disadvantage, which will lead to most emperors being inferior like the Ming Dynasty. On the contrary, no matter where the Qing Dynasty selects the best, no matter where they are born, everyone is good! I'll just give you an example. Emperor Jing of Han first made Liu Rong, the eldest son of Li Shu, crown prince in 153 BC. Two years later (151 BC), Empress Bo was deposed. (150 BC) deposed The crown prince Liu Rong. In April of the same year, Empress Wang was established, and then Liu Yan was made crown prince as Empress Wang's concubine, and his name was changed to Liu Che.
Why did the Ming Dynasty establish the eldest son of Shu and then no concubines be born? Naturally, it was in order to smoothly inherit the throne, after all, the deposed prince who had no fault shook the country, so he was stored later. When the emperor is fortunate to be an empress or successor, there should be contraceptive measures to ensure that the crown prince has succeeded to the throne and avoid embarrassment! Before King Yan ascended the throne, Zhu Gaozi was the prince of Wang Shizi, and naturally he wanted to be made crown prince! Zhu Zhanji was made the emperor's grandson in the Yongle Dynasty, and Zhu Qizhen's establishment as the crown prince was the emperor who wanted to lift up his mother and depose the empress!
In ancient times, emperors would depose the former empress before they were born, or after the eldest son of Lishu, they would no longer spoil the empress. An example is that Emperor Jing made Liu Rong crown prince, because he basically did not favor Empress Bo. Later, if Liu Che was to be made crown prince, he had to skip other princes, so he first made Wang Meiren empress. In this way, Liu Che was promoted to the eldest son.
Generally speaking, if the first empress is in the childbearing age (the emperor will not be too old), if there is no concubine, she will not be in a hurry to establish a prince, but is in a hurry to establish a prince, it is estimated that the empress will not have to give birth. Most importantly, the sons born to the general empress before the throne of the middle palace are not legally concubines, and the queen does not have children, which is a small probability event in history