That maybe Yona’s uncle (don’t remember the name), was the one responsible for her mother’s demise (hopefully not), and that’s probably the reason King il murdered his own brother ( & didn’t even feel guilty about it).
Wow! Revenge sure is a vicious cycle, ain’t it? If my theory is true, then yona’s Uncle killed her mother for vengeance for his own wife, Il killed him to avenge his wife, and soo-won killed Il to take revenge for his father. And Yona saw it! Now Hak is the one boiling with the seeds of revenge.