Fan Sizhe had become Fan Jian's legitimate son because his mother, Liu Ruyu, had given birth to him after she had been made the second wife. After Fan Jian's wife passed away, Liu Ruyu was promoted to the position of wife, and Fan Sizhe became the legitimate son. Although Fan Sizhe had an older brother before him, he died young, so Fan Sizhe became Fan Jian's heir. Therefore, Fan Sizhe was a legitimate son, not a bastard son.

Fan Sizhe had become Fan Jian's legitimate son because his mother, Liu Ruyu, had given birth to him after she had been made the second wife. After Fan Jian's wife passed away, Liu Ruyu was promoted to the position of wife, and Fan Sizhe became the legitimate son. Fan Jian only had one wife and one concubine, so Fan Sizhe was the only heir to the Fan family.
Fan Sizhe was the legitimate son. Fan Sizhe's mother, Liu Ruyu, had been made the official wife of Fan Jian and had given birth to him, making him the legitimate son of Fan Jian. Fan Jian only had one wife and one concubine, so Fan Sizhe was the only heir to the Fan family. Although Fan Sizhe had an older brother before him, he died young, so Fan Sizhe became Fan Jian's legitimate son.
Fan Sizhe was Fan Jian's legitimate son. His mother was Liu Ruyu, Fan Jian's concubine, but after Liu Ruyu was officially made the second wife, Fan Sizhe became Fan Jian's legitimate son. Fan Jian only had one wife and one concubine, so Fan Sizhe was the only heir to the Fan family.