[CamperBob2]

Same here. Apple's process for dealing with lost or stolen cards is just insanely stupid. Why in the world do I need to 'validate' the existing card, which I no longer have, in order to add a new one?

What possible security or business justification could exist for that? What does it even mean to 'validate' a card you've been billing successfully for years?

(Spoiler: in case this happens to anyone else, the secret turns out to be disabling family sharing on the account. It will then let you remove the old card and add a new one, after which you can re-enable family sharing.)

[duxup]

At some point someone needed to add a layer of security and like so often picked something that they assumed someone would know.

I don't have a magic solution but all this using random factoids about us as identity verification seems to be a big hassle.