Just a quick note to say hi! Your aunt's daughter is your cousin. Your aunt is right. There are many grave syndroms and illness that occur more often if you marry within family. There is more likelihood of genes with the disease to pass to the children by both parents if they are related. I know because that is what happened in my family. So, you are young. Go see a genetic doctor that can explain to you the medical issues. I have seen the illness of some kids in my family when cousins marry or even uncle and niece. Try to find someone else and forget your love for your cousin. You are young and time heals love trageties in time, which is better than a child with many issues.
God bless you in your decision.