When I include both of the following roles into one role, it fails, but if I remove the _family_manager include, it works.
role :some_kind_of_admin
  includes :_family_manager
  includes :_family_reader
end
  role :_family_manager do
    has_permission_on :families, :to => :manage do
      if_permitted_to :manage, :children
    end
  end
  role :_family_reader do
    has_permission_on :families, :to => :read do
      if_permitted_to :read, :children
    end
  end
privileges do
  privilege :manage do
    includes :create, :read, :update
  end
  privilege :read do
    includes :index, :show, :search, :list
  end
...
end