Your sister is a dragon, and you just casually ask a dragon slayer to live with you. Not to mention her new father the slayer doesn't know about. Great idea, really ;).
I don't get how easily bro turned into some de facto leader. He tells everyone to come down, and somehow everybody immediately chills out? Impossible. Not to mention how nobody even discusses their opinion normally except him and the one obnoxious guy. People just don't behave this way.