Fu Fangzhou didn't start out doubting his identity.
In his memory, his parents were always busy, and he thought this was normal. After all, they managed such a big family business, and it was understandable that they didn't have time to accompany him.
It wasn't until the birth of his two younger brothers, seeing his parents' love and care for them, that he began to realize his position as merely an onlooker, recognizing his parents bit by bit.
Through his two younger brothers, he finally realized how neglectful and indifferent his parents had been toward him.
As a child, Fu Fangzhou thought it was parental favoritism.
Later on, as he grew up, seeing the resemblance in appearance his brothers had with the parents, and himself in the mirror bearing no resemblance at all, he was dazedly aware of something.
So parental favoritism was normal after all.
Although he suspected, Fu Fangzhou did not express this, nor did he tell anyone about it.