Busted :D

I have a classmate and we never had a chance to talk to one another but everytime I look at him he still looking at me. I was seating in front of him and I just ignore that look because I know its nothing.

Small world, we both have a mutual friend, I'll name this girl Cah, she is a sister in law of Tian who is my classmate and felt staring at me. Tian saw our photos on Facebook and send Cah a private message. Cah told me about the message and said:

Tian: Sis are you friends with Joanna(my second name)?

Cah was asking me if I know Tian.
I really don't have an idea who is this Tian but after a minute I've found out that he is my classmate from my first subject.

Then Cah Replied: Yes bro why?
Tian: Oh she's my classmate in Literature. And She's my Ultimate Crush.

Cah was giggled telling me about this, I was surprise but I don't know what to say.

He added: I always staring at her because she was seating in front of me.
Cah: Should I tell her bro?
Too late Cah told me about it, so that's why he stares at me, I don't know what should I feel. But I am willing to be a friend with him.

What should I do? I thought he's a serious guy. PS: He's in 30's of age