My sisters boyfriend?

well honestly you sound like you have the mindset of a child. and you are one. relax too, your sisters 12 it's not even a real relationship. calm down. the fact that her "boyfriend's dad" is a cop is a good thing. It most likely means he'll be responsible. So by threatening him you just made life worse on your sister.

well you gotta give your sister time with her boyfriend i mean if you had a rally cute girl im sure you wouldnt want your sister butting in to it. but i mean i dont think her boyfriend could be too much of a bad kid i mean his dads a cop? yeah im sure id be being good lol. i know you want too look out for your sister but i dont think you need too get into it inless somthin bad does go wrong or she is lookin upset lately. and his parents shouldnt be getting involved in your life so i doubt you have anything to be afraid of with nott getting along wit the law.

You don't have to harras or be violent to get your message across (I know it can be the easier to do sometimes) but if he hurts your sister just make sure he apologises to her, but ask him not force him, but at the end of the day she is 12 I wouldn't start being protective till she's like 15 or 16

Well, I have 5 older brothers, and a boyfriend. But the first week we started dating, my brothers, (of course) tried to scare him so he wouldn't do anything stupid. Which, (of course) I didn't exactly appreciate. I think you should just back off and let them be. BUT, if he does break her heart, don't be afraid to have a talk with him. But don't break out you're fists, that will just be trouble for you, and you're sister.