Is this wrong or right?

Well, I'm a pianist and i been playing for years. theres this guy that i know and he's my best friend's brother. one day him and i were in a piano room and he played my favorite song (moonlight sonata by Beethoven). After that we started talking which is good because him and I are both quiet. And i think i really like him and i don't know if i love him, but he has a girlfriend. its not like he's married to her but do you think i should talk to him like he's single? I really like this guy and it feels like the piano brought us together, and he thinks i have pretty eyes! what should i do? :/