Two children cap...

[GrannyMac]

That makes more sense. Artificial Intelligence went for the Artificial Insemination explanation. I expect yours is more common.

Yes, it's often grandparents.  It's usually better for a child than going into the care system, but unless they are relatively young grandparents, it must be tough.  We couldn't cope with a young child or a teenager now.  

[Dextrous63]

How does one forge the require documentation so as to claim one has a child, when one has not?

I have a cunning plan to boost my income. 😬😬

[klondike]

You probably need to forge the paperwork to get on universal credit first...

[Ashy]

I've heard it alleged that immigrants claim that their children were born abroad, and borrow some kids if the authorities want to see them.

Although I would never do it, I wonder how easy it is to register a birth and get a birth certificate, when no birth has taken place.