I still don’t get the mom thing, is she mc’s real mother or not?

Oh yeah...

Probably?

The mom is his bio mom she even said there was a DNA test to prove it was real

So the dad basically chose the younger based on his similar looks to his as the heir and the mom got obsessed with the elder sibling so much that she hated her younger child!!! What’s wrong with this family!!! No wonder the real hajin was so off