I like my best friends sister?!?!?!?!?!?!?

[Johnson]

I'm a guy and I like this girl who is my best friend's sister. I have told my friend that I like her. He is cool about it. I'm sure that a lot of guys who like her that he knows about. I would say that me and him are best friends though, so that mite be different. I'm sixteen and I've never liked a girl other than her before! I'm never shy around girls; except for her.
If you like a girl do you just tell her? Do people do that? Should I do that? I like her a lot! I don't know if she likes some one else, but she has never done anything to show that she doesn't like me. I always thought she liked me, then when I started likeing her I didn't want to get my hopes up. I know her more than any other girl. Should I tell her? Our familys are really close, we would still have to be around each other if she doesn't like me. How would I tell her? I have so many questions, please start talking to me people. Girls and guys.