The situation with him is actually a great real life example of this scenario. Remembering a past conversation, he does very strongly believe that the earth is 6,000 years old now that I think of it...
He has his issues like anyone else, but overall he is very sweet, kind, generous, a loving dad, etc., and obviously my sister thought his very loosely held beliefs were a non-issue for them. Except now, they're not so loose or without effect.
For example, the godmother thing aside, he seems to think God will solve everything. Ask and he will provide sort of stuff. They were having difficulty having a baby back before my niece because my sister has polycystic kidneys. What this means is her kidneys are both the size of footballs and there's not a whole lot of room for anything else, if you know what I mean. They also don't work well and were down to 70% functionality at this rate. Doctor said not to try any more because the chances of death for the fetus and my sister were high at the worst, or she'd lose even more function at the least. My sister was crushed and really wanted to try so they compromised and tried just until her birthday. They lucked out and she conceived, and after a month in induced labor in the hospital my niece was born prematurely but both survived.
I'm obviously delighted they both pulled through, but in my brother-in-law's mind, God gave them a miracle and they should go for #2. My sister lost 50% more of her kidney function (this means her kidneys will now completely fail in the next few years as opposed to 10 or so more) and she nearly died, but he was still adamant that #2 was a given because they got #1 thanks to God. This led to some nasty fighting with my mom and between them in particular. Maybe some people can overlook or live with someone who holds beliefs in extreme opposition to their own, but when it comes to kids or these kinds of decisions, you can't count on just being able to hold them at arm's length anymore.
Sorry for the long story.
His cousin thinks he is the embodiment of piousness because he memorized a few lines from the bible. He tries really hard to be aloof and important, but the guy is a non-starter in life basically. I feel kind of bad for him, to be honest.