Girl is younger than the boy in a relationship :|

I have a crush on this guy for about 2 years already. He is a brother of my close friend. I knew him even before but did not feel anything for him but when I discover who he really is by and by, I realize i already like him. I think he likes me too but he's shy to talk about it because he knows that there is an age gap. In your opinion, is it okay to date younger men? By the way he is 3 years younger than I am.