Should I beat up my girlfriend's brother?

[Anonymous]

This past Halloween, I was invited to a party by the woman who is now my girlfriend. We were just friends at the time, but I really liked her and felt kind of protective of her. At the party I was introduced to her younger brother (~17 years old), and despite his politeness when we first met, I pretty quickly figured out that he's a world-class jerk. He'd invited a gang of friends to the party too, and kept showing off in front of them the way teenage idiots do. But the real problem is, he was super rude to his sister (now my girlfriend) and once he even punched her in the arm, not violently like he wanted to harm her, but just hard enough that it probably hurt. I wanted to beat up the little punk then and there, but it was my first time at her house and I'd just met her parents, so I just simmered there for a minute. I think he realized I was kinda pissed at him and he went away. My girlfriend's reaction to all this was serious, like they weren't just joking with each other, but she seemed to be used to this kind of thing. What do I do if he hits her again when I'm around? I don't want to piss off her parents, but that kid had better wise up.

Updates

+1 y

So the answers I've gotten so far are pretty decisive, but the thing that really puzzles me is people saying it's a unreasonable question. He's bigger and stronger than her, despite being younger, and clearly wasn't doing this as an expression of endearment or humor. Bullies need to be taught with the only language they know.

[DevikaButts95]

Oof. I feel bad for the girlfriend. You're just assuming there's somehow a problem without any indication from your girlfriend that it actually is a problem, and you immediately want to punch this kid for this to the point you genuinely came and asked on GaG if you should beat up her brother. Like you just straight up jumped to that conclusion right away.
Huge red flag. I'd paint you as an abuser more than the brother.

[Asker]

Really? The whole reason I asked the question was because you don't hit women, ever. It doesn't matter if it's your sister and it doesn't matter if she's older. I'm worried he does this all the time and it's unacceptable. Contrary to popular belief, telling violent boys "it's not okay to hit" is utterly useless. And clearly she didn't find it funny. I said so in the question.

[DevikaButts95]

First off dude, get off your high horse man. There are rational reasons to hit a woman, like self defense for example.
Second, you're assuming out of nowhere that his intentions are violent even though you yourself said he punched her "not violently like he wanted to harm her", like you're contradicting yourself. Like this could easily be playful or just roughhousing, siblings do that. Even if your sister wasn't happy about it, like intentions could very well still not to to be to just violently assault his sister.
Third, you're basing this off just literally one incident, and decided "wow that's evidence he does it all the time and I should beat him up", like how dude.
And believe it or not, yes you can actually end the problem by rationally discussing it. If it doesn't and you resort to violence that's one thing, but you're just jumping straight into the violence.
You're an abuser dude. I feel bad for this girl, I wish I could warn her you're about to assault her bro.

[Asker]

Well, you made a ton of good points but I still don't get why you think I'm an abuser. I only wanted to protect her from harm, this is ridiculous. Also, self defense is the ONLY rational reason to hit a woman and that's clearly not at play here, so irrelevant.

[DevikaButts95]

Well you said you don't hit women ever so like, lmao. But I agree irrelevant.
Because man look, someone who springs that quickly into violence is a red flag. Beyond so many assumptions you made and how quick your temper is, the only thing I'd takeaway if I saw you do that to my brother (well if I had one) is: He didn't like what my brother did, so he beat him.

[ricochet100]

I think it would give a bad impression of you, make you come across as someone who is quick to violence. She might not want you to step in, and if she has grown up in a violent home it’s probably not what she is looking for in a guy. Just my opinion but I’d dump a guy if he did that.

[Anonymous]

Me and my brother playfully hit each other all the time, if my boyfriend were to even lay a finger on my brother for that then I would dump his ass.

[jerijay]

Why don't you let her defend herself after all he's her brother they're family.

[unomilkis1]

No, chances are their interaction is somewhat of normal, and if your girlfriend were to think her brother was a problem she would take it to her parents. Don't over step your boundaries

[killer4212]

Eh don't try to be a hero.