When you take decisiion to marry u just cant think about 2 of u, but for entire next generation. Keep that in mind. For your mistakes someone else should not suffer, that too unborn child will suffer life long and their children too.. and so forth.
No no. Brother sister marriage is bad, prohibition. Adv Raj malhotra has answered properly. This is not love. This is only lusting for body. You two have s*x with both's agreement and all love will be gone after that.
Only 2 ways if you want to marry her, either you will have to convert your religion or you will need to make both the parties her parents and your parents become ready for the marriage
The law states that
The marriage is possible if custom or usage governing each of them permits,
Even in the case of prohibited relationship or sapind relationship. So make families to get agree for the marriage or change the religion.
Now talking about medical issues related with the sapinda marriage, there is 4-5% more chances of genetic diseases like color blindness and many, consult a doctor for that