Offering Vassalization

[eternalkanus]

So, I'm an independent king and after a series of murder plots I've managed to get my young grandson on the throne of a neighboring independent duchy. I had assumed this would give me the ability to make him my vassal, but the stacking penalties mean it seems impossible to offer to vassalize someone unless they're either a de jure vassal or two (or more) ranks below you. Is this the case? Can you not vassalize a family member, even if they're much weaker than you and love you, just because I'm only a king, and he's not in my realm? If so, is there any way to mod diplomacy to increase the worth of high relations?

I'm using CKII+ if that matters.

 

[Lorehead]

If you press a dynast’s claims instead, you get him as a vassal. You can try raising your relations by enough that he says yes, or wait for his heir to love you enough to say yes. You could keep murdering, until his duchy ends up in the hands of a relative in your realm. You could conquer the de jure title. Finally, you could cheat using the console.

 

[NewbieOne]

It seems easy for AI to diplovassalise, compared to how hard it seems for a human player. I've been able to vassalise people being their de iure ruler only with a difference of two ranks. This includes being unable to diplovassalise OPM dukes as a multiking and their de iure liege, possibly same religion, different culture. I had a difficult time vassalising people as a king but as emperor I found it much easier to vassalise dukes than counts were when I was king.