Well, if you want a felony on your record and want to spend 5 or more years in prison, I would highly advise against it, along with all the charges of probably $100,000 or more. You'd be pretty screwed just for wanting to get your penis wet inside some girl you've known forever because she's finally hit puberty. You need to date girls your OWN age or older, plain and simple, it's the law.
I am with ninjadude!!! If You want a criminal record go for it!Watch court tv there is enoughg cases on there like that! To my knowledge there is only one State that allows you to have sex with some one under 16, and some are 18! And, there is nothing wrong with you liking your buddy's sister! You might just kind of drop a hint to him that you like her...VERY subtle! BUT don't "bang" her until she is legal!