How to make peace with other factions as a Vasall?

[Dagalexxus]

Apologies if this a dumb question but I cannot seem to figure out how to make peace with other factions as a Vasall of a kingdom.
Is there a way somwhere? The option in the diplomacy section of the kingdom overview is always greyed out and now I am struggling with a three front war which is basically just me charging from one place to the other.

Can someone give me a hint?

 

[somaholiday]

You can't.

 

[Soulcharger]

Massive executions.

 

[ombror]

same for me, can't use my influence to do that. Clan tier 4, maybe we need tier 5 ???

 

[metafa]

Massive executions.

This

 

[Crowquills]

Massive executions.

And I've been letting them go thinking that raising my influence with them would help.... jeez... time to let the heads roll.... again