Hi drwbe,

You can't do that (I mean, in Piwigo 2.8).

What you do is:

1) create an album "for my family", set it as private, give access to group "myfamily"
2) with plugin LocalFiles Editor, in the local configuration, add :

<?php
$conf['inheritance_by_default'] = true;
?>

3) create a new album "for my family / Peter's birthday party" : this new album will automatically be private and permission granted to group "myfamily"

please tell me if it fits your need :-)