Virtually every lord in Christendom worth his salt maintained a large collection of dependents at his home. This was called the familia; it translates roughly to household. Kings possessed the familia regis, or royal household. The familia included both aristocrats and commoners, though the former receive greatly more attention in the sources, especially the household knights - the king's full-time, personally loyal warriors. We know the most about the household knights of John I and Edward I, but the concept is as old as knighthood itself. Not all knights possessed land, especially young knights at the beginning of their careers. To serve a lord - especially a king - was a perfectly respectable way to sustain one's self and make the sort of contacts necessary to a career as a military aristocrat. If you managed to impress, he might give you land outright or arrange your marriage to a wealthy widow or heiress. Numbers fluctuated, decreasing in peacetime and increasing in wartime. But, to put it in perspective, Edward I's household knights peaked at a strength of something like 600 during wartime.

In war, household knights essentially made up the hard core of the army, unconcerned by length of service or scarcity of pay (or, at least, less so than a pure mercenary). There is some evidence that by the time of Edward I they had begun to function as pseudo-staff officers, arranging logistical matters for the army. Though these men served in peace and war, we know much less about their peacetime activities. Some were household officers; that is to say, they supervised some aspect of the domestic realm, whether it be the stables and horses or finances or wine and other provisions. It is apparent that others were literally farmed out when not needed - temporarily assigned to one of the king's manors for their sustenance.