What should i say to the boy that loves me ?

I'm 14 and there is this boy in 11th grade that really loves me and I know he is not messing with me because I got to know him and he is a real angel but from before I met him I fell in love with a different boy that I still love wee are like the same and I know he cares about me but I'm sure we will never be together ! And the boy from 11th grade knows I love someone els and he knows who he is but he won't live me no matter what and I really like him but I don't want to brake his hart ! What should I do ???