[IshKebab]

The use of the parent is an example. In reality it would be some official age checking provider (maybe the government).

[spragl]

Yes. I think that wahtever organization that issues your passport, would be a natural choice for setting this up.

But nothing prevents it from being a private company, although I cannot see a sound business model for it. Also it would need to project great credibility for customers to trust them with their information.