One brother doesn’t share or give up decision making well. The roles are intended to be project manager rather than dictator; the person is still expected to solicit opinions and delegate tasks to others. He gets frustrated really quickly when he doesn’t get his way entirely and will get to a point where he doesn’t hear other people’s perfectly reasonable views.
But it’s been this way forever, it’s his personality. He knows it. A few of us are pretty good at calling attention to his behavior in a way that he doesn’t feel attacked by and he’ll chill out. One just goes toe to toe more aggressively with him and that tactic works sometimes too.