In a pickle

In my playthrough only 3 big factions left, valandia, northern empire, and aserai. Sturgia keeps getting doubled teamed by valandia and NE, and southern empire are down to one last castle. I was advised to increase relations with these almost wiped out guys so I can recruit when making a kingdom. At this rate, by the time I get these relations high enough they will be wiped out… what can I do?