you do know that he is not even allowed to be kissing you right? you are way under age and he is an adult according to the law so any type of physical contact he has with you is considered to be statutory rape and child molestation. it is not just that he cannot have sex with you. he can't do any type of physical contact with you at all.
it is normal for young girls to fall in love and start dreaming of marriage but it is not normal for an adult man to fall in love with a child. i know you don't look or feel like a child, but he should know the law concerning you and should not be forming a close relationship with you at your age. there are just too many temptations in it.
what do your parents say about this relationship? and his parents, what to they say?
as for him wanting to marry you, you are just beginning to form the personality you are going to have when you are an adult. between now and when you turn 21 you are going to change the way you feel about things and the way you look at things many times over. so there is no way he is taking into consideration the person you might turn out to be. you will be totally different when you grow up from what you are right now, so how can he really know if he is going to want to spend the rest of his life with you since he doesnt yet know how you are going to be?
in addition to that, you are going to see him change a great deal from now until he is about mid-twenties or early 30's. that is when most guys begin to really mature. so, you don't know what or who he will turn out to be.
that is the real reason why young people are encouraged to wait until they are older to think about getting married. it is very rare for a young couple who falls in love in their teens to stay in love and remain together as they mature and change in attitude and personality.
still, with all of that said, it is still normal for you to start dreaming about being in love and getting married at your age. just have the sense to realize that neither of you might actually make it to that point with one another.