“Where are the children?”
He would always ask her that. [Italics mine.]
For Eddard to expect Catelyn to know the children’s whereabouts at all times seems a bit incongruous: a woman of Catelyn’s rank has many vital household management duties and (as we learned from Waymar Royce’s wet nurse) is far from a full-time childcare provider. However, I don’t remember Eddard asking Catelyn about where the children are again (we’ll see how good my memory turns out to be), so this might be a character feature that, like Tyrion’s somersaults, was quietly let drop.