Gran Torino is about Walt, a retired Korea war veteran. His wife dies and he has to live alone. He’s then later on invited to a garden party hosted by his Hmong neighbors. He establishes a friendship with the daughter of the family, Sue and later on with her brother Thao.
Walt says he feels like he has more in common with Thao and Sue’s family than his own. I think this is because his family thinks of him more like a chore than a family member, while Thao’s family takes him in and appreciates his presence. Even though Walt doesn’t understand their beliefs and way to be, he still enjoys being there with them. He even lets Thao borrow his Gran Torino for a date. This shows how much Walt enjoys taking care of and being friends with Thao. Also, this could be how he is trying to make amends with himself for not wanting to spend time with or understand his own sons. Therefore he takes the role of Thao’s father and tries to teach him how things work and how to be a real man. He even ends up writing the Gran Torino to Thao in his will.
When the Hmong gang shoots at Walts neighbors house and rapes Sue, he decides to take revenge. Thao wants to kill them but Walt has other plans. Since he already knows he’s sick and feels like he can’t be redeemed, he sacrifices himself so the gang goes to jail for a long time. This shows how much he cared about Thao and Sue, he was willing to die for them. I don’t think he even would do the same thing for his own family, because Walt seems like a man of principles and since he isn’t even treated like family by his actual family, but by Thao and Sue like a father, makes them way more important to him.