As mentioned above, your relationship doesn't come under sapinda relation so you are legally free for making a alliance. But, you have to look once towards society that whether this relationship is acceptable or not. As your relationship is somehow brother and sister relationship which are not acceptable to our society. That is one matter. Another point is as, you did not mention about your financial status? Both of you are working or not as it is very important point in today's world. If you are economic independent then you can handle your own situation. Otherwise, your future life would be hell. You should consult your family member in this regard. You should not take decision hurriedly. Marriage is done in life once. So, you should be careful before taking any decision. Oftentimes, It has been seen that love is just body attraction and after marriage boy don't want to take any responsibility especially giving birth of baby. So, be careful and select mature life partner.