You seem to be at the crossroads so to speak. You are at the right age to go for it, but young enough if you aren't careful, you will let your heads get in the way of your hearts. We let that happen when we were your age. We know better now, but much too much water has passed beneath the bridge. Looking back, we would have did things much differently, and probably went for it. Would we have ultimately made it, I don't know. Even though you may be cousins, you are still only human, and we all have our failings and differences. We are very much alike, but have some noticeable differences of attitude and opinion as well. We are still very close, and even after not being around each other all these years, are still close, and enjoy each others company very much.
If I were you, I would keep this on the down low, until such time as you two can find a way to be together. If you let your family basically "forbid" you to be together, will they guarantee your future happiness for you? No. They will continue to manipulate you in other areas as well. You two will have to make yourselves happy, a manipulative and overbearing family cannot and will not do it for you.