My ex phoned my kids school up and said the same thing one day. I had a Family Court order with specific terms on it for our custody arrangement and it was sealed by the court, but my ex said I had forged it. Pretty easy thing to say.
I have full care of my 2 kids and their mother has nothing to do with them at all. If I left the country I could take my kids but if the court order said that she was to see them so often, I would be in breach of the order if I failed to make them available.
If biomum is the real deal, she should have filed for breach of orders years ago, even back when Z was in the news in Townsville with the Soldiers and Camp Quality.
It's probably a fake biomum and if it's not fake, she's no real mother to Z as she has never been in her life. AB didn't steal Z from biomum.