Real simple question on faction relations.

Let's say I'm playing vanilla M&B, and I'm a vassal of the Nords, and I roll over to Rhodok territory and waste some peasants. Nords aren't at war with Rhodoks, I just do it for ****s and giggles. I'm now at -3 relation with the Rhodoks.

How do I get that relation back up to zero? When I talk to lords at rest in castles, I get no option to make peace or anything. Is that because I'm already in a faction? If so, seems like a horrible oversight to let you lower relations but never raise them.

one that's been mentioned is to rescue lords from capture. Maybe buy it off when you meet a rhodok lord (that is weaker than you) in the field only?