Atheist stepdad here. Does that count? 
My boys have both attended church with their bio-dad. He belongs to an end-times arch-conservative baptist church. If you know who Arnold Murray is (televangelist), you know that church. Very fire and brimstone, OT, no shellfish or pork, and they believe this Murray guy is to be one of the two ‘witnesses’ of the end times…In other words, batshit crazy.
My oldest has told me that he’s basically there for the food. He’ll believe anything you tell him as long as you feed him at the end of it. No firm convictions, always the path of least resistance. He’ll make a good politician some day.
My middle son, however, disturbs me. He aspires to be a zoologist (he’s a frickin genius), but he is being fed all sorts of things about ‘not making plans, for the kingdom is nigh’ type stuff. He also is told that the salvation of all of his friends and family are his responsibility. So he is always sad. Hell, he’s worried about MY parents because they are Catholic. More than once, he has come back from a church meeting to our house and cried himself to sleep over it.
As I said, I’m an atheist, though I’ve never really made an issue of it to them. Especially around here, where them mentioning to their friends could have serious results for our family. I will believe when I have reason to, not before. I’m sure that if God i worried about me, he’ll sit me down and have a talk with me before the whole hellfire thing. If he decides I’m not worth the time, well, I don’t have any regrets about how I’ve lived my life.
I try to be supportive- I’ve never once poo-pooed his faith (I know that it would be seen as an attack on his dad as well, and I don’t do that). I just try to reassure him that no one has all of the answers, it’s okay to not know, it’s okay to doubt, and that that I love him no matter what.
But I worry. His belief does not seem to make him happy. He’s a good kid, but he’d be one without God in his life too. And I’m afraid that his need to believe will turn him away from confronting the facts that are part of a formal education, and he will end up never leaving Arkansas, never graduating high school, and never rising above menial labor, just like his dad.
It bugs me the more because their mom and I set such an easy path for them to follow. They know that they are loved no matter what, and that we would die to protect them. All that we ask in return is a good showing in school, incidental help around the house, and manners at the table. They can believe whatever they like- but I wish that it made them happy. That is does not is a constant concern for me. I can only hope that they will grow out of it.