If I remember correctly, Hajin is the second child, while the white-haired one (Baek Ha-yeon) is the first child, so they are siblings. It's just that because the white-haired one was sickly, his position was replaced by Hajin. So that's why Hajin is called fake because Hajin actually replaced his white-haired brother. Hope u understand. In essence, Hajin's mother was mentally ill because she hated Hajin so much and preferred to love the white-haired one. The white haired guy's name should have been Hajin, but it was changed to Ha-yeon, and vice versa for the MC
But isn’t he in high school. He’s older than hajin but in HS? Is this because he was so sick he did his school later?
Yup, Your guess is correct
Omg I hope mc gets away from this family
Spoiler pls why did that guy call mc fake I think it's not for the reason mc thinks it's is did the og guy take original hajins place like maybe in the story real Hajin died n another kid which is the hajin in og novel took his place?