Most Helpful Guy
Haha ok. Well it seems that he likes you its just that he's too shy so say it. Men are also scared of rejection. Try get his cell number and start messaging him. After a while you might start saying hello in the corridor and things like that. After a while try go out together. Like to the movies or something similar just the 2 of you. If you are able to start talking more in person and grow your friendship then eventually he will open up about his feelings.
Most Helpful Girl
He seems like he's curious about you and he probably wants to get to know you but doesn't know how to approach you yet. If he doesn't approach you after a while then maybe you can ask his sister to maybe help you out with him and tell her to ask him what he thinks of you. She should be able to help you out or give you suggestions on what to do.