so im reading 2 theories in the comments cause honestly it's just "i read this somewhere" vibes....
#1 theory: is Hajin is the Dad's kid out of wedlock (so by another woman) Blonde dude is the dad and mom's kid.
#2 theory: Hajin is the the Dad & Mom's son but he's actually the second born not the first born. Blonde dude was actually frail or something related to health issue so dad made Hajin the first born and heir and other reason is that he looks more like him (lol idk)
honestly the end result is rather than hating the dad more the mom hates hajin more (???) hahaah
take these two theories with a grain of salt hahaah
tysm!! makes a little more sense now. also ikr thats so weird like hate the father not the innocent kid
i’m still so confused after reading everyone else’s explanations in the comments what is going on. like ik they were switched at birth but who’s is who’s bio kid???