Brother/sister argument

So this past Saturday I wanted to go to this friends party. I’m alone at the house bc my family other than my older brother is out the country. I asked my brother if I could go out and I told him that I didn’t know what time I would get home. He got upset and threatened to tell my parents. It wasn’t a big deal but at the same time I hated that he did things he wasn’t supposed to do when my parents aren’t home but yet I HAVE to ask for permission? It seems really unfair and I got so upset I never came home. I hate that he doesn’t follow the rules but yet I have to? I haven’t done anything wrong at all. All I do is work, school, sleep, and occasionally go out with my boyfriend. But my parents know for the most part I don’t do anything bad. It just upsets me a lot that he thinks what he’s doing is right. Then all I ask is to go to one party, idk when I’ll be back bc idk when it ends so yea. Am I overreacting? Sometimes I really cannot be around him. Like you’re about 25 and still acting a damn child? I get I’m kinda acting like one but he’s supposed to be the adult here. You get me? Ya feel? One major thing though is that he’s a married man and doing things behind his wife’s back and she doesn’t even know. I hate that he does such things because why did you even get married in the first place if you knew you were going to be doing the exact same things you’ve been doing even before the marriage. I rlly don’t think he truly understands what marriage means. Sometimes I like to think that I know more about love than he does bc I’m faithful to someone who isn’t even my husband yet. I’ve most definitely been with this person a long time (almost 2 yrs) and I would not dare ever cheat or do things with other guys behind his back. You know? I hate that he does those things. I hate it. It gets me so upset ☹️