Tough call: on principle i am a big believer in telling ppl you like them- otherwise what is the point?, but you have to ask yourself do you like him for him, or because he is like your X? Also, if he won't date you because of age difference then i say tell him to go to hell and find someone new.
However if you like him for him and it isn't set in stone that he won't date you, then i say flirt and see what happens. If your X gets mad or he doesn't bite then you have a new problem, but some answers.