Your sister is right! You're too young to be getting caught up in stuff like this. Don't go anywhere near this guy - he's aiming for your pants (whatever he says)
You have to make your own decision about what is right fr you, but she may well be right :)
Be wise and do what is right. Be foolish and suffer the consequences.
I think you should listen to your sister, because she cares about you.
Don't do anything with that guy.
As an older sister myself, I can guarantee you....she is right....and you should always listen to her! Both of my sisters have come to me as adults and said how much they wished they had just listened to me......