I told my crush's sister that I liked him?

Become an adult. Instead of texting his sister in hopes that she will tell him about your crush, why don't you try calling him and talk to him.

Of course, if you want to play games, just send him a text pretending that you think you are talking to his sister and tell "her" about your crush. He will get the text by mistake and your problem will be solved. He will know how you feel and you will avoid having to initiate any direct conversation with him.

Or you could just grow up and stop the games as I said at the beginning. Your call.

"That's so cute" = awww.

Which means she just thinks it's cute, not really real.

I suggest you back off on this.

Is he older than you?

Either that or she thinks that you are not his type in my opinion.

She will tell him... Trust me.