In many cases, vassals did have their own vassals, in a process called subinfeudation. There is a link below, but it does not give as much information as I would have liked to find.
Anything the king wanted.
The vassals were in a relationship of mutual obligation with their superior lords or kings. They provided an oath of allegiance and support in exchange for land,...
A vassal was a person who swore allegiance and homage to a lord. In exchange for this, he got property consisting of an estate or estates from which he could get income as the serfs who lived there...
A vassal was a person who had gone into a mutual obligation with a monarch or feudal lord. The monarch or lord got the vassal's allegiance and homage. In exchange the vassal got land and protection....