Absorbing Vassals

[Pico2014]

What options do i have for absorbing a vassal?
I only know the absorbing vassal decision - manual states its also possible through diplomatic transaction.
But what are the requirements? No way they will accept my offer. I‘m at 55 relationship, 9 regions vs 5, stronger army, more authority. But not thaat much (65 to 42)

Playing denmark, want to absorb jutland.
I got 1 absorb decision early on but it failed. Since then nothing. I‘m in turn 41.

I assume they are simply too strong/big (compared to me) to accept diplomatic offer, its -207 points^^

So.. what can i do? (Of course i could just conquer them) but thought it would be more elegant to absorb them. But that seems to be fairly difficult/nearly impossible for me?!

[Surt]

improve relations, buy a region from them and try again.

[Pico2014]

Thx. Will do so.
On first sight trying to absorb in this situation seems to be far more expensive than just go fighting.

[Surt]

It gets cheaper when relations are high, but I also often think lets just show them the pointy end of the spear.