We do, in fact, know what that phrase means from a legal perspective in the English. I believe it would cover anyone with legal or de facto custody of a child. Wherever somebody with legal custody, for example, transfers that custody—even by saying, you take care of my child for this period of time—then the exemption would apply to that person. Cases in which it wouldn't apply are those in which that custody hasn't been transferred.
On May 31st, 2012. See this statement in context.