Is Gladstone no Scrooge heir?

[Daniel van Eijmeren]

In Barks's "The Doom Diamond" (US 70), the Duckburg officials plan 
to remove Scrooge's fortune to Fort Knox, presuming him lost in a 
terrible storm the South Pacific.

There's no mention of Donald and the nephews as being Scrooge's heirs.
A reason could be that they may be presumed lost, too. But there's no
mention of Gladstone Gander at all, either...

This seems to mean that Gladstone is not considered a heir of Scrooge, 
at least not inherently.

--- Daniël