Do not understand claim rules

[jguy100]

I'm saving and reloading a file while I figure this out, so sue me

I decided to pursue a claim against a rival kingdom for one of my courtiers. After winning the war, I realized he became king of the land independent of me. I was hoping to have him still be my vassal afterwards!

The save file I'm working with is about 3 months before the end of the war. I've tried a few different things, and no matter what, he still becomes an independent ruler of the kingdom after the war:
1) I gave him mayorship of one of my cities
2) I gave him bishopship of one of my bishropics
3) I straight up murdered him (ended war with no gains)
4) I married him to one of my widowed vassals

What do I need to do so that I stay his liege after the war?

 

[SigurdStormhand]

Give him a Feudal title.

 

[Serenity84]

A king can't be liege to another king. You need to be an emperor for this to work

1) I gave him mayorship of one of my cities
2) I gave him bishopship of one of my bishropics

You want to give him a castle so he stays feudal

 

[Naughtius Maximus]

Just remember if you want to grow your realm only you or your heir should press claims for same or higher tier realms.

If this is a lower tier realm, they will become your vassal if you meet any one of these criteria.

1. This title they are claiming is de jure part of your title (say, duchy of Salerno when you are King of Sicily.)

2. They are already you vassal. Courtiers are not vassals, so that means they need to be landed. Give them land, preferebly a castle. Or city if you are merchant republic.

3. They are of your dynasty.

 

[_Perun_]

Giving him a feudal title isnt necessary. Cities and bishoprics works just fine. They are a bit more problematic in the long run but if you want to have a tidy realm, revoking the kingdom is advisable, ideally taking advantage of religious revocation, less ideally through the intrigue focus.
And, of course, as mentioned above - whatever title you gave him it will work only if you are an emperor yourself.