Roger that!
I have several thoughts with backstories/problems/arcs they could bring to the table:
1.) A human family with land near the borders of Velt and Thaln, this plot of land is small and was granted as a favor for the family's service in the War of the Red Flag as an afterthought, but now it is generating more and more grief for the King and Queen- settlers are encroaching on Velt's forests, cutting down trees and hunting their game. The noble's armsmen are too few in number to put a stop to this, and the family's eldest child has been sent as a hostage to Velt to prevent an invasion while The Fated Child is sent to Thaln's capital to enlist in the Rose Knights, and ingratiate the family to the Queen once again. If only the youngest could learn a more conventional fighting style than the Battle Dancers of Reon...
2.) The Envoy of the Queen has returned from a mission of healing to the southern city of Ahta, a place that is within the borders of Thaln and bound to it by ancient treaty but also fiercely, dangerously independent. The Envoy is trained to serve the Goddess Mayon as an Acolyte to her Second Prophet, Marcos who preached that those who healed with magic should do so at the cost of themselves during the time of the Plague of Red Death. An outdated notion, but one that still survives to this day in more "backward" parts of Thaln.
3.) The Fool grew up among the disciples of the Green God in the north. Insular and haughty, these folk pay their tithes to the Queen and expect to be left alone. Fleeing a crime that has Outcast her from the community, the initiate arrives at the heart of Thaln with a request- that their mother's mother's mother's service to the Crown be remembered, and they be allowed to squire for the Iron Rose Knights
Like I said, I don't plan to hijack the thread with their backstories, but I'd like to fit in fairly well with the story.