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Personally I think the age gap is too much for you guys now. The number is not what matters its the maturity of each individual. As people mature their wants and needs change. However, I don't know the people involved.
Now, what I would do is make sure your both on the same page about having feelings towards each other. Then simply mention to him that your interested but will need time to grow up and mature so that you can be on the same page as him.
Don't forget that you have plenty of years ahead of you and by the time you get a little older, you might realize a relationship really isn't what you want anyway. Especially so young!