@reiver

You wrote:

Or, a parent giving money to their child.

On a tangent: #Taler not only supports P2P payments, but offers a privacy-preserving mechanism for age-restriction, built-in into the coins, as well.

Parents can give their children coins that are usable only for items up to - say - 12. The proof of the requirement doesn't reveal the actual age of the payer.

See our paper: https://www.taler.net/papers/esorics2022-age-restriction.pdf