It's infuriating, but if it's your brother, unless he's jeopardising an important priority in your life in a way that affects your life opportunities and/or wellbeing/health, ya should probably tolerate it somewhat. Like explain why what he did is a bad thing and let it be. Family discount. At least it's not your parent that's acting up.

Anyway, I am just talking out of my ass here, free advice, and all that. I don't blame you at all, I'd be pissed too.