request for genetic counselling

Dear Doctor,

i am contacting you on a verry personal concern,i request your kind help in answering my query.

I am deeply in love with my second cousin and we are planning to marry,i am 25 years old and she is 20 years old ,now she is the daughter of my mothers elder sisters son,(that makes second cousins has we have common great grand parents only..?).unfortunately she has a brother who has some birth defects (no heriditery disease,some defect at the time of bith...no proper skull formation) and her parents are no way married into the family.they are of complete different family line .,same with mine.Now my relatives are worried that i have an unhealthy child with her,has she already has an unhealthy brother Plus we are second cousins.

I know there is some degree of risk by marrying her,but i belive its of a verry small percentage (3-5% ??),we are deeply in love and i cant wreck her on this simple issue.
i request your professional advise taking into consideration our situation.