Damn... why don't they just move out though? If they own the house, they could sell it and simply not say anything to his brother, then when the new owners come to the house, they would kick him out. Same if they just go rent somewhere else. Grandma is more difficult, though if the teacher really pays for his tuition and living expenses, he could work part time during uni and use that money to send the grandma to a facility where she gets taken care of. Grandma would be taken care of, shit brother would get a real nice tase of reality and become a homeless persons with no skills, either manual skills or people's skills.
But damn... I know that his mom is fairly broken, is tired and wants to give up, but she is also willingly putting shackles around him. "Just leave us behind", "Please. Don't leave me. If you are going, then bring me along." He might not love them dearly, but they are still his family and he seems like someone with a sense of responsability, so "Just leave us behind" is using his guilt to make him stay. "If you are going, then bring me along." makes killing himself a lot harder. Your life is your own, but if it gets attached to someone else's, then you would end up killing two and he probably doesn't want his mother to die. Maybe she didn't say those thing to shackle him, but that was the outcome...