Say a Jew marries a goy, and no one wants to convert. It happens, sure. (Although, dear goyim, it's never too late.) So both go about their lives, worshiping as they are used to... until a child comes. What does one do?
One possible solution is to split up the children. I'll take the first one, honey, and you can have the second. Or you take the girls, I take the boys. But then, you'll always have the lingering feeling, did you pick the right one? That's just not good.
Well, this is exactly what the Yarmy family did. Older brother Don was raised Catholic, like his mother. He later became Don Adams and starred on Mel Brooks' "Get Smart", talking into a shoe and what not. Younger bother Dick was raised Jewish, like his father. He later became an actor as well... and appeared on "Get Smart" in a small role.
So did it work out for the Yarmy family? Who knows. Of course, splitting the children up is not the only option.
You can agree that the decision doesn't have to be made now, and spend the child's formative years quietly indoctrinating them. Worshiping a zombie nailed to a cross doesn't make much sense, does it?
Sounds like a plan!