I apologize for the oversight in the responses. Thank you for pointing that out. Here are the correct responses:
Cheonson wants to leave his family, but John wants to stay with his. - Cheonson wants to leave his family to serve his country, while John wants to stay with his family in The Unbreakable Code.
Cheonson loves his family, but John does not. - Cheonson holds his family in high regard and wants to leave them to fulfill his duty in Cheonson and the Admiral, while John cherishes his family and wants to stay with them in The Unbreakable Code.
Cheonson learns lessons from his grandfather, but John does not. - Cheonson learns important lessons from his grandfather, Admiral Yi Sun-sin, while John does not have a prominent mentor figure in The Unbreakable Code.
Cheonson was always brave, but John was afraid in the beginning. - Cheonson demonstrates bravery throughout the story, while John initially struggles with fear before finding courage in The Unbreakable Code.
The key differences between Cheonson and John lie in their motivations, relationships with their families, mentors, and levels of bravery demonstrated in the two stories.