I think..
When Myungha went to get captured by the police(?), he assumed Chungha’s identity so that he(Myungha) could take on the crimes of their father on behalf of Chungha (since the whole family would be punished for colluding with the second state councillor or smthing like that) because Myungha wanted Chungha to start a new life with his maternal family, not as ‘kang chungha’ but with a new identity. I think they just had ‘kang chungha’ (actually Myungha impersonating chungha) ‘die’ so that myungha himself could have a new start?

Heyy, isn't kang chungha myungha's little brother? Why are they saying he died? Isn't he supposed to have returned to his mom's family or sth? Sorry Im just confused here