Should i tell his sis i like him?

I kind of agree with lisadon. If you think you can trust her to not say anything until you want her to, then go ahead and tell her. It would be good if she was your wingman b/c she could tell kris all the things you like, and stuff about you, so he knows what you're like and what you like and stuff. So yea, if you think she will keep it to herself if you want her to. Good luck! I hope you and Kris work!