Despite his actions, he seems to be able to feel remorse and regret for Tsugumi & Otone
He just saw his home, his loving parents, his things burn down into ashes right in front of him, who wouldn't be emotionally unstable after seeing that? Both him & his brother got the short end of the stick, though with some variations
The problem where both of'em won't reconcile with each other is most likely because of his secret/regret that he won't tell his own brother about the real cause of their last family member's (in the house) death was because of his own words
In short, because he's the reason Otone died he probably doesn't like being near Tsugumi anymore (Not because of hate, because of his regret). He knows his place, he still loves Tsugumi as a family but he can't really bare the guilt that'll appear every time he sees him
Poor guy
And yeesh, this is pretty dark