You're a good sister :-) but you should have a little faith in the system. There is a young man's defence available for circumstances exactly like these and, if the police get involved, make sure that they (and your brother's lawyer) are in full possession of all the facts. Do not ever lie to the police or to defence lawyers however tempting it may be to alter the truth. Also, you're wrong about the rape and underage thing. There is no defence at all, no mitigating circumstances, to rape but there are a number of factors which are taken into consideration when it's statutory rape, as is the case here. If the young lady in question alleges non consensual sex and relies on her age as the basis of making the claim, she could easily go to prison for attempting to pervert the course of justice. Law makers aren't as stupid as you seem to think although I accept that you may not be thinking clearly just now. No one is getting prosecuted for this one. The offence of having sex with a minor is always tempered with the circumstances of both parties and an 18 year old and a 15 year old having consensual sex falls completely outside the intention of the law. You gave the girl a slap, she gave you a fright (and your brother got sex and a fright) and unless this girl is truly stupid, it will all end now.