I'm not going to get my brother food
Why don't you want to get him food?
Because he's a lazy asshole.
You aren't required to feed or take care of everyone, you can say no if you need too.
But I am worried that if he's hungry he might die.
It's good of you to be concerned about your brother. If you think things can get that bad, you might want to get a third party involved by having an expert talk to him about his lack of motivation.