The MC's Dad, the person he was accused of killing, was not the previous King. The MC's Dad was the previous King's brother so the MC was the previous King's nephew. Since the previous King had no children, next in line was the MC's Dad and if the MC's Dad passed away, the MC would then become King. After he was accused of murdering his Dad, he was sentenced to Death and his aunt, the MC's Dad's and previous King's sister was put on the throne. The aunt is related with the siblings who took in the MC as a slave and it6s heavily implied that the aunt and siblings conspired to have her brother, the MC's Dad killed and blame it on the MC.
The MC is the rightful heir to the throne and I think that's what the ML is trying to correct, make the MC King by removing the aunt from the throne by force. But if the truth that the ML didn't kill his dad, and the aunt/current ruler was involved comes out, they won't need to use force. The aunt and brother killed the Mc's dad, aunt wanted the throne and the black haired guy wanted the MC, the sister later found out and helped her brother cover it up.

Ok spoil me pls
My theory: lister (the black haired brother) killed the previous king and pinned the blame on Mc and his sister is helping him and somehow they wiped his memory, and are trying to make sure he doesn’t remember, the new sorcerer is helping him ? And gjord has sth to do with the old sorcerer getting “sick” and new sorcerer and Ml are both trying to help him?? But these black haired siblings are evil
And pls on god tell me lister gets tortured too or sth I’m mad