Parents write policy from whatever happened most recently, and if you are first, that means you. One bad night out becomes a rule, and the rule stays long after you have stopped doing the thing, applied to siblings who never did it at all. The rule was not written to punish you, it was written because nobody had seen the problem before.

Worth knowing when you are deciding what to risk, since the consequence is wider than yourself. It is also fair to say to your parents, once, that a rule made about you four years ago might not fit your brother. They have probably not thought about it.