Damian - You Asked.
The title "Earl of the North" is a historical reference that has ties to the ruins of Penstair. The territory appertains to the Free Wilds of Deshir. At the time of this manuscript, the titled lineage for Halwythwood is vacant - therefore, the two domains are loosely "connected" - Halwythwood looks to s'Valerient, and the caithdein for King's Justice in the absence of am actively endorsed ruler.
Originally, each lineage in a clan had an Elder - appointed by concensus, or claimed, by right of aware power. These Elders form the council. Many decisions for the clans are human ones, not rooted in Paravian Law. The council and chieftain therefore handled such matters, by vote or unanimous concensus - which way depended on the gravity of the issue.
The drifters are clan based, and do inhabit the free wilds - just not a forest landscape.
The appendix in the US edition of TK clearly defines how power descends…the title of Caithdein does not necessarily follow the earl's line of inheritance. Often, it might. You are viewing the rare circumstance when the power is split between Barach and Jeynsa - the reason Why is detailed in that appendix…if you don't have access to the appendix, it's a logical extension of what's happening in the historical setting of the story.