Would this work?

[CybrSlydr]

So, I'm almost to 1100 in my save and I've managed to become an Emperor of Denmark with the following Kingdoms under my control:

-Norway
-Sweden
-England
-Ireland
-Pomerania

Is it possible, or even a good idea, to grant Kingdom titles to 5 of my vassals and then transfer all of my remaining vassals under the appropriate King? All the English Jarls to the English king, all the Swedish Jarls to the Swedish king, etc?

 

[Turbofjes]

Yes.

 

[Naughtius Maximus]

If anything granting the title does that automatically.

 

[CybrSlydr]

If anything granting the title does that automatically.

No kidding? I wondered if that was the case.

EDIT: So, is it a good idea to do this?

 

[stavern]

Giving all titles out will give you less taxes since you only will collect from 5 kings instead of 30 dukes. The dukes who earlier considered you their master will now have a new king master. You will up with 5 powerful kings who may start a civil war. If you hit vassal limit better to give out one king title. Expand some more until hit limit again and give out a second title.

 

[CybrSlydr]

So, I can, but bad idea. Thanks.

 

[Legeis]

.....so as with all things in ck2... its complicated!

Vassal kings can be a really useful tool if you have a big empire and are approaching your vassal limit. They can also be useful in certain political situations where you are having a hard time maintaining a high enough option from your vassals but that will be super situation dependent.

Some negatives are taxes. Levy size. and it being hard to manage your vassals holdings (think duke A obtains county that is part of duke B's de jure but you cant fix it cause duke A is a vassal of King A and Duke B is a vassal of King B.) Also kingdoms can have realm laws that differ from the laws of your empire.

If I can I prefer to at the very least to only give out kingly titles once I have managed to pass appropriate laws to forbid internal vassal wars. Though ideally I only like to give out kingly titles once I can give them out as kingdom viceroys.

one really useful way to use them is if there is a kingdom that is outside your Empires De Jure and also makes out one of your Empires boarders. I will sometimes give that kingdom out even b4 I have vice roys.

Because:
#1 non De Jure vassals will have a lower option of you. By having a Vassal king you only have to manage your relation ship with that 1 king rather than all the vassals of that kingdom.
#2 powerful vassals will often enter wars with neighbors to expand their territory. By handing out a kingdom on your boarder your vassal will expand your realm as he goes to war with your neighbors.
#3 While a little messy you can always revoke the title to get it back if the vassal starts to get to powerful. I try to only do this about once a generation otherwise you may get assassinated!

 

[stavern]

I like to have dukes in control of two duchies each but that require feudal and a bit of planning from the beginning. And even if you give the title out as agnatic primo after two or three generations the vassal may change it to gavelkind. So where you once had one vassal now have two.

 

[majdavlk]

It might work :
If dejure kingdom of a duchy doesn't exist yet, the Duke can be transfered to any king, if the kingdom exists, it needs to be transferred to that king.

No such restrictions apply to counts and barons.

Is it a good idea :
Not really, but how bad depends on which dlcs you have enabled.
With taller feudal hierarchy, you get reduced taxes as it needs to go through more middle men ( unless you managed to stack a lot of tax bloodlines, i like to do that.)
The amount of levies should remain around the same, but i have a suspicion that levy calculation takes into the equation only the government of your direct vassal and not his subvassals.

Youre also making your vassals more powerful and they will be able to faction more and each individual direct vassal will have more strength. It might be good if you want them to expand for you, but youre risking stability a little bit. I prefer either spamming merchant republics under king tier republics or tribals, giving all of my spare counties to a nomadic vassal and i keep all barony tier vassals in direct vassalage.

 

[Sunshine Moon]

A couple of reasons I like to consolidate to king-tier vassals (though there are certainly several drawbacks, as pointed out above) are:

-They quickly become strong enough to put down religious/peasant revolts without you having to lift a finger.
-They let you raise a large amount of vassal levies in one spot (at any point across a large area) rather than having to bring lots of smaller armies together, which gives you a much faster response time
-If you're trying to convert counties to your religion, the more layers of vassals you have beneath you, the more people can be using their court chaplains at the same time and the faster it will happen, especially with a proselytising religion.

I also think it benefits tech spread through your realm in the long run, since kings get more tech points than dukes?

 

[MK1980]

partitioning the realm into half a dozen super vassals is the lazy solution. much easier to handle a few powerful guys than a horde of dukes or even counts.

they'll also help propagating your culture and religion (if that's your goal). you only have to educate 1-2 generations of vassal king kids to establish the proper culture and they will happily perform the busywork of educating the kids of the dukes and counts to spread it to the lower ranks.

main downside is the somewhat lower tax income as was mentioned by others. you can make up far that by turning some of the vassals into merchant republics. in your case, i'd probably make ireland a merchant republic. maybe also pomerania.