The Crown Prince knew that Fan Xian was a prince.

Fan Xian asked if the Crown Prince knew about the assassination, but he didn't mention it. Therefore, I don't know if Fan Xian asked if the Crown Prince knew about the assassination.

Fan Xian asked if the Crown Prince knew about the assassination, but the information was not clear. Although the plot of Fan Xian's assassination was mentioned, there was no clear answer as to whether Fan Xian knew the Crown Prince had participated in the assassination. Thus, it was impossible to determine whether Fan Xian knew or not.

The reason the Second Prince knew Fan Xian was a Prince was because when the Qing Emperor had summoned Fan Xian, the Crown Prince, and the Second Prince to dine together, before he left, the Qing Emperor had instructed the three brothers to enjoy the delicacies and hinted at Fan Xian's identity. Although Fan Xian had not understood the meaning at the time, the Crown Prince and Second Prince had already understood the Qing Emperor's meaning. Thus, it was certain that the Second Prince knew Fan Xian was a Prince.

The reason the Second Prince knew Fan Xian was a prince was that during a meal, the Qing Emperor had instructed the three brothers to enjoy the delicacies and hinted at Fan Xian's identity. Although Fan Xian had not understood the meaning behind it at the time, the Crown Prince and Second Prince already knew of Fan Xian's past. Thus, the Second Prince knew that Fan Xian was a prince.

The reason the Second Prince knew Fan Xian was a Prince was because when the Qing Emperor had summoned Fan Xian, the Crown Prince, and the Second Prince to dine together, before he left, the Qing Emperor had instructed the three brothers to enjoy the delicacies and hinted at Fan Xian's identity. Although Fan Xian had not understood the meaning at the time, the Crown Prince and Second Prince already knew that Fan Xian was the Qing Emperor's son. Thus, the Second Prince did not mention the specific details of Fan Xian being a Prince.

The Second Prince knew that Fan Xian was a prince. When the Qing Emperor summoned Fan Xian, the Crown Prince, and the Second Prince to eat together, before he left, the Qing Emperor instructed the three brothers to enjoy the food and hinted at Fan Xian's identity. Although the specific details had not been mentioned, the Crown Prince and Second Prince already knew that Fan Xian was the Qing Emperor's son.

The Second Prince knew that Fan Xian was a prince. In " Celebrating Years," Fan Xian and the Second Prince were half-brothers. They were both children of the Qing Emperor. Although the exact time was not explicitly mentioned, Fan Xian's identity was when the Qing Emperor had gathered Fan Xian, the Crown Prince, and the Second Prince for a meal. Before the Qing Emperor left, he had instructed the three brothers to enjoy the food and hinted at Fan Xian's identity. Although Fan Xian had not understood the meaning behind it at the time, the Crown Prince and Second Prince already knew of Fan Xian's past. Thus, it was certain that the Second Prince knew Fan Xian was a Prince.

The Second Prince knew that Fan Xian was a prince. In " Celebrating Years," the Qing Emperor once instructed the three brothers to enjoy the delicacies while eating and hinted at Fan Xian's identity. Although Fan Xian had not understood the meaning behind it at the time, the Crown Prince and Second Prince already knew that Fan Xian was a Prince. Thus, it could be concluded that the Second Prince knew Fan Xian was a Prince.

The Second Prince knew that Fan Xian was a prince. In " Celebrating Years," Fan Xian and the Second Prince were half-brothers. They were both children of the Qing Emperor. Although the exact time was not explicitly mentioned, Fan Xian's identity was when the Qing Emperor had gathered Fan Xian, the Crown Prince, and the Second Prince for a meal. Before the Qing Emperor left, he had instructed the three brothers to enjoy the food and hinted at Fan Xian's identity. Although Fan Xian had not understood the meaning behind it at the time, the Crown Prince and Second Prince already knew of Fan Xian's past. Thus, it was certain that the Second Prince knew Fan Xian was a Prince.

When the Qing Emperor had gathered Fan Xian, the Crown Prince, and the Second Prince for a meal, the Second Prince had already known that Fan Xian was a Prince through the Qing Emperor's instructions and hints. The exact time was not mentioned.