Subinfeudation

Subinfeudation is the practice of a noble giving part of their fief to another and elevating that person to a lower noble title who swore loyalty and fealty to them. In the Third Imperium, all oaths of loyalty and fealty are sworn to the Emperor, and nobles must maintain their fiefs intact and in good order for their heir.
Aslan clans practice subinfeudation with clan assets extensively, but even Aslan nobles of the Imperium are not allowed to do so with fiefs attached to Imperial titles.