The benefit of digital things is that they can be copied much more cheaply than physical things. There’s perhaps migrations and upkeep though.

On the technical side perhaps the shared nature of this helps - if you can have something replicated so that you and several other members are all running replicas there’s a

On the non technical side, take some photos and print them on good paper. Print out stories on paper.

That doesn’t cover video and perhaps other things but it’s simple and does actually work for lots and lots of stories and pictures. It’s also immediately doable right now without anything new.

Looking/thinking about this and all the digital photos that are spread across multiple phones and accounts led me to My Family Archive. I haven’t pursued it yet, but they seem to have thought about some of this.