Putting kids first explicitly means, to me at least, showing it to your spouse and to your children that she (your spouse) is second only. It may not be deliber

Putting kids first explicitly means, to me at least, showing it to your spouse and to your children that she (your spouse) is second only. It may not be deliberate, may not be conscious, but it will manifest in sooner or later. (How frequently it will, depends on how strong this decision is.) Children not only need loving parents, i.e. parents who love THEM, but also ones who love each other, a couple a model. It's needed for them to want a family, it's needed so that they don't see having children as an obstacle in the way of their personal happiness. So sometimes, it's beneficial to put the children second, beneficial from their point of view as well. But in general, I don't think there are too many situations when we have to think about who comes first (unless we marry an asshole :) ).