to be honest the big brother is emotionally unstable cause of his sickness yet I dunno which of the 2 brothers has the biggest problem ╮(￣▽￣)╭ but the big brother really confused me going back and forth in his decisions until chapter 3
I feel like it is completely reasonable for him to be conflicted. The older brother said he was dying when you first see him. That would scare anyone. I'm sure he feels guilty about his younger brother being forced to take care of him to the point where the younger brother doesn't have a life of his own. The older brother's whole life also probably revolves around Yuzuru. He has no one else close to his age, and he obviously doesn't go to school. There's no way he wouldn't be conflicted about letting go of his lifeline (basically). Also, the comment about the robot that does whatever he wants leads me to believe that the older brother was the one to tell Yuzuru not to spend time with Koutorou when they were younger. He probably regrets that to some extent now, realizing just how much he isolated his younger brother. I find him more pitiful than hateful. He's scared and trying to cover it up with sarcasm and bluster. On top of that he has this younger brother who basically threw away his own life for his older brother's benefit. There is probably an excessive amount of guilt there, but he doesn't want to lose the person who cares the most about him either.
Maybe it's unrealistic, but I'd like to think there is some sort of middle way; that lets all three keep something. Or even find something they had never expected to. :)
I thought the brother was goung to be more of a manipulative asshole. But it seems like he himself is a bit conflicted whether to keep Yuzuru close to him or let him go. I find the God angle very interesting