Liu Ruyu said that Fan Er was the legitimate son.

[Liu Ruyu did say that Second Fan was the legitimate son.]

Liu Ruyu had indeed said that Second Fan was the legitimate son. In " Celebrating Years," Liu Ruyu was Fan Jian's second wife, and Fan Jian married her and gave birth to Fan Sizhe. Although Liu Ruyu had a high status in the Fan manor, Fan Jian did not promote her to the official wife, so Fan Sizhe was called the legitimate son.

Fan Sizhe was Liu Ruyu's son. Liu Ruyu was Fan Jian's second wife, and Fan Jian had officially married Liu Ruyu as his wife. Therefore, all of Liu Ruyu's children were Fan Jian's legitimate sons.

Fan Sizhe was the son of Fan Jian and Liu Ruyu. He was considered a legitimate son because after Fan Jian's wife passed away, Liu Ruyu was made the second wife and gave birth to Fan Sizhe. Even though Liu Ruyu had a very high status in the Fan manor, Fan Jian had never promoted her to be the main wife. Instead, he treated her as a concubine. Fan Jian didn't go through the relevant procedures, indicating that Liu Ruyu was the first wife of the Fan family, so Fan Sizhe was considered the legitimate son of the Fan family.

During the Qing years, Liu Ruyu's son, Fan Sizhe, was called the legitimate son because Liu Ruyu was Fan Jian's second wife. After Fan Jian's first wife passed away, he married Liu Ruyu as his second wife and gave birth to Fan Sizhe. Even though Liu Ruyu had a very high status in the Fan manor, Fan Jian did not promote her to the main wife. Instead, he treated her as a concubine. Therefore, Fan Sizhe was considered the legitimate son of the Fan family.

During the Qing years, Liu Ruyu's son, Fan Sizhe, was called the legitimate son because Liu Ruyu was Fan Jian's second wife. After Fan Jian's first wife passed away, he married Liu Ruyu as his second wife and gave birth to Fan Sizhe. Even though Liu Ruyu had a very high status in the Fan manor, Fan Jian did not promote her to the official wife. After Fan Jian's first wife passed away, Liu Ruyu was made the second wife, so all the children she gave birth to were considered Fan Jian's legitimate sons. Fan Jian didn't go through the relevant procedures, indicating that Liu Ruyu was the first wife of the Fan family, so Fan Sizhe was considered the legitimate son of the Fan family.

During the Qing years, Liu Ruyu's son, Fan Sizhe, was called the legitimate son because Liu Ruyu was Fan Jian's second wife. After Fan Jian's first wife passed away, he married Liu Ruyu as his second wife and gave birth to Fan Sizhe. Even though Liu Ruyu had a very high status in the Fan manor, Fan Jian did not promote her to the main wife. Instead, he treated her as a concubine. Therefore, Fan Sizhe was considered the legitimate son of the Fan family.

During the Qing years, Liu Ruyu's son, Fan Sizhe, was called the legitimate son because Liu Ruyu was Fan Jian's second wife. After Fan Jian's first wife passed away, he married Liu Ruyu as his second wife and gave birth to Fan Sizhe. Even though Liu Ruyu had a very high status in the Fan manor, Fan Jian did not promote her to the official wife. Fan Jian had officially married Liu Ruyu as his wife, so all the children Liu Ruyu gave birth to were Fan Jian's legitimate sons.

During the Qing years, Liu Ruyu's son, Fan Sizhe, was called the legitimate son because Liu Ruyu was Fan Jian's second wife. After Fan Jian's first wife passed away, he married Liu Ruyu as his second wife and gave birth to Fan Sizhe. Even though Liu Ruyu had a very high status in the Fan manor, Fan Jian did not promote her to the main wife. Instead, he treated her as a concubine. Therefore, Fan Sizhe, Liu Ruyu's child, was considered Fan Jian's legitimate son.

During the Qing years, Liu Ruyu's son, Fan Sizhe, was called the legitimate son because Liu Ruyu was Fan Jian's second wife. After Fan Jian's first wife passed away, he married Liu Ruyu as his second wife and gave birth to Fan Sizhe. Even though Liu Ruyu had a very high status in the Fan manor, Fan Jian did not promote her to the main wife. Instead, he treated her as a concubine. Therefore, Fan Sizhe, Liu Ruyu's child, was considered Fan Jian's legitimate son.