the truth is you can marry your second cousin and have perfectly normal children, the only risk in defects of such a Marriage is if your children grow up and also marry their cousin. So it's a generation thing. Marrying your cousin is in the Bible, Isaac was sent by Abraham to marry his brother's daughter Rachel which in turn was Isaac's first cousin.
I mean with a 99.9% chance of problems you can still have no problems, and iirc you only have something like 6% chance of complications with your first cousin vs like 3% with a complete stranger not really worth worrying about imo, and is perfectly legal in many countries (tho socially stigmatized) but the risk does grow exponentially the closer the parents' dna match afaik, so I would recommend against bearing children with direct family because at that point it's probably too much of a risk.
as for whatever the bible says it also mentions a global flood, the parting of a sea, and a talking burning bush so it's not really worth referencing
you know they used to test peoples blood when they got married to see if they were related or not, but they have not done that for a very long time so there are a lot of people who are Married and do or don't know that they are related, then most them have had children who also married a distant cousin, there is probably a 0.1 percent chance that we are all related.
I would have my DNA tested if got Married, and find out if I was related to my spouse or not. When you are in love you probably wouldn't care though that is how love works.