If that’s true, then that’s just disturbing because that would make Jian also his relative and they have a sexual relationship!
I wouldn't put it past that Hajoon bastard. By the way, I think President Yang - Jian's biological father is the grandfather's long-time subordinate. The dude was being kicked by the grandfather at the restaurant where he supposed to meet Jitae in chapter 14. At first, I thought Jian's real father is the grandfather, that would explains his tolerance to that witch. But now I thought maybe that witch is his illegitimate daughter. Jitae just kept quiet for the family's reputation and wanted send to Jitae's mom from that messed up family.
I was also thinking about this Hajoon-Suryeon thing, and tbh this story (at least Jian's story) is disturbing enough already to have this plot twist... So I wouldn't be surprised
Suryeon is just some power hungry woman. Her only relationship to the grandfather is through his now deceased son, president Baek, and Jian, a father and son tie. But it has now been revealed that she lied about that so the deceased president baek is not really his father! Which is sad because his marriage with Jitae’s mom was ruined over nothing! The grandfather only tolerates her because she knows and done too much that could ruin the company if it ever gets revealed. Including, Jitae’s mother’s murder! Which is why the grandfather gave her his dead son’s old position as president! That position was always meant for Jitae and that’s why it was vacant for a long time, until Suryeon got caught in the act of killing jitae’s mom. He wanted to put a leash on her with the thing she covets, if that makes sense.
If that then the grandfather is stupid. That witch ruins his son, dragging his reputation through the mud, abusing his grandsons, doing so many dirty works that could wreck the whole company, maybe even have a hand in his only son's death aka Jitae's father.
He is dumb! Because he only cares about reputation! So there is a lack of human decency with him. That’s why Jitae went forward and threatened him and the company! For his mom and Mieum, who was/is an innocent victim dragged into their petty games over the company.
That Hajoon punk and Jian's mother have the same hair color, and they kind look alike. Could it be he's her relative?