Slitherine

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?!

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

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

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