In Australia, this wouldn’t even be a criminal matter. You would have to go to family court and file a recovery order. My ex withheld my two chn last year, for 6 mths. And not a damn thing anyone would do unless I went to court. As I became homeless 4 weeks after he took them, I had no home to recover them to. My ex also used the mentally unstable line, unable to care for the chn. Family break ups are messy, and sadly children can become weapons. And the damage being done to these poor wee ones just breaks my heart. They didn’t ask for this, what kind of relationships will they have in their future because of this, even when they are found and returned to dad, this is not going to end. Praying for their safety, and that the parents both grow up and realise they only have a limited amount of time with their children...stop wasting it.