I think a lot depends on pre-existing situations. In many couples that are still together, the mother is the defacto childminder, doing the bulk of the caretaking of the kids while the dad occasionally "babysits" and when they split up, this situation remains. before I divorced, I paid my niece to watch my kids while I worked and I cared for them at night. their mother spent way less time with them. after separating, it was several monthes before my first 4 hour visit and took a year to slowly 'introduce' the kids to me.