bro..sorry to say, but this is gonna be messed up  (both in ur family and genetically) if it is a conservative family, its gonna be almost impossible to convince them and leaving any family hardships. and genetically, her genes and ur genes are both 50% the same. (since she got 50% for her father, and u got 50% from ur mother, which are passed from ur grandparents - so are very similar).  and when you want to start a family, ur will be sharing similar genes as ur cousin, and this causes too many imperfections. but there are many cultures and people around the world still practice this so u can research about this there. first thing is convincing your parents. and mama.