[Cryptography] Secret sharing for family members

[Henry Baker]

In these days of 'digital estates', where each of us
controls a large swath of digital accounts, there
appears to be a need for safely sharing secrets with
family members -- e.g., for medical and/or estate
planning purposes.

Here are some desiderata:

* don't want to trust a single family member
* family members probably not security conscious,
  so may inadvertently disclose other family
  member secrets
* may need some sort of 'majority' capability
* ability to 're-key' -- i.e., 'refresh' secrets
* ...

Are there any products/services that *safely*
handle these situations?