That doesn't matter - because of the low statistical probability of his/her mate also possessing those same genes.
Rather, one's mate usually possesses (recessive) genes for a couple dozen entirely different conditions.
Except in cases of inbreeding - then otherwise rare conditions become rapidly common.
Regards,
I have seen other articles at FR that pointed out that because Islamic society make it very difficult for boys and girls to meet and form marriages, that often first and second cousins ended up getting married as they only had opportunities to meet each other. This is a danger in any insular society.