User blog comment:Robert Mc Roberts/Rebuilding Europe: Restoring Power to the UK, France, Russia and Spain/@comment-3242795-20120530201412/@comment-3300047-20120530201935

It was used in real life in a number of cases.

Commonly, the hier to the Kingdom would be given the ability to rule another smaller nation to prove himself.

Some examples:

In Spain, the ruler of two sicilies was the Spanish hier.

In France, the ruler of Anjou was the French hier.

In the UK, the prince of wales was the British hier.

In Austria-Hungary, the viceroy of Lombardy-Venetia was the Austrian hier. etc.

Plus, the colonies had a good degree of autonomy, so "granting indepedence" means letting your royal hier rule it on your behalf.