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