Vassal count inheriting three foreign counties - why warning?

[Basquenoel]

Hi everyone.

I'm playing as 'Petty King of Brittany' (Duke) and invited an Irish heir (first in line of succession to three Irish counties) to my court in order to expand my realm. In line with everything I've read on that issue, I granted him a county in Brittany so that the three Irish counties will fall into my realm once the current Irish count dies.
See CK2 Paradox Wiki:
-> Succession#Inheritance_Conflict
-> Expanding_your_realm#Arranging_for_vassals_to_inherit_foreign_territory

Now what I don't understand is why the alarm "Vassal Inheritance Warning" pops up?
Normally, he should be inheriting the three counties into my realm, as he will keep his current same-tier county as primary title, right? I am duke, he is count, and he inherits only counties (no duchy).
Or does it play any role that he would inherit three counties at once while only holding one at the moment?

Or can I just ignore this warning because the warning-AI doesn't take into account same-tier inheritances as falling into my realm?

 

[fg109]

The wiki is correct in this case. Think about it; what happens to the county if your vassal dies right now?

 

[Basquenoel]

Oh yeah thanks, obviously the warning is about my vassal's potential death and his brother (Irish count) inheriting the county of my realm, not about losing the county in case my vassal inherits in Ireland. So I need to hope that my vassal gets a child soon who would inherit his newly granted county so that it remains in my realm.
And I only thought abouting making sure that the other way round - my vassal's older brother in Ireland dying first - nothing could go wrong about my vassal inheriting into my realm.

 

[BuddyLove]

Yes, so engineering that scenario is important- make sure your vassal is married and load him up with concubines if Tribal.

And if possible plot to kill his brother or antagonize him into a dual, or raid his lands to try to imprison him.

 

[Spaninq]

If you're *really* desperate, seduce his wife and hope you don't get caught.

 

[Basquenoel]

So, in the meantime, he got an heir (no more vassal inheritance warning).
As I didn't want to to wait too long for him inheriting in Ireland (his brother got a child), I pressed his claim and won the war for one of the Irish counties which is part of my realm now.

A new question then, just to make sure:
If I now revoke his primary title (in my original realm) so that he only controls the Irish county, will he still be my vassal? More generally, can I influence his decision on which of the counties is his capital/primary? (if he would switch, I could plot to revoke his title and spare me the penalty)

And another question for another heir I have at my court:
When pressing claims, the tier where I landed him in my realm doesn't matter or does it?
So, if I build a new barony (castle) in my capital county and grant it to someone, will my realm expand once I successfully press his claim abroad or will he become independent?

 

[BuddyLove]

Yes he would still be in your realm.

No you can't really influence him much- unless you can give him the duchy in Ireland (AI vassals tend to make their capital inside a Duchy they own). Otherwise they are kind of random and there's no button to ask them to switch.

Could goad him into rebelling so you can strip it without penalty.