Some of them are your councillors, some your vassals, andsome knights are even your sons and heirs.
Of course, this isn’t a perfect method - sometimes you might not have any valid applicants.
What is a knight’s prowess in Crusader Kings 3?

Now that you know how to get them, what do knights actually do?
Knights have a stat that comes into play when fighting called prowess.
This skill reflects how well they perform in individual combat, as well as duels.

Basically, you want your knights to have as much prowess as possible.
Every point of prowess gives a knight 100 damage and 10 toughness.
By comparison, each levy has 10 damage and 10 toughness.

Knights are super strong soldiers who can really beef up your chances of victory.
There are ways to keep your knight corps strong though.
you could increase your knights' effectiveness by investing in the martial lifestyle with your leader.
It’s also possible to increase the total number of knights under your command.
This can be done using lifestyle perks like Kingsguard, or by increasing your level of fame.
Earning more prestige gives you extra knight slots, allowing you to deck out your armies by even more.
What else can you use knights for in Crusader Kings 3?
It’s often good to use the ‘force’ and ‘forbid’ options when managing knights.