In How to Find the King, I looked back to my experience as a member of the Grand Canyon Crew for insight into how a band of men discover who among them are noble, and who the noblest. The Grand Canyon Crew was remarkable for its fraternity. We were all equals; if there was to be a Head Boatman, he would be primus inter pares.
This sort of fraternity within a band of brothers is the feudal ideal. Its archetype is the Round Table. Arthur wanted to be, and was indeed, first a brother among brothers, and only in virtue of that brotherhood would he want to be their King.
Most bands of brothers are not as fraternal as the old Grand Canyon Crew, let alone the Round Table. Some in such bands are nobler somehow. What distinguishes the nobler brothers?