House Bracken hails from Stone Hedge, with much of their domain lying across the fertile lands of the Red Fork. House Blackwood is in Raventree Hall, located north of the Red Fork. As Lord Baratheon mentioned, both houses are quite powerful, In fact, both families can assemble larger armies than their regional wardens, House Tully. The Targaryens merely chose the Tullys to be wardens of the Riverlands since they had the good sense to bend the knee to Aegon the Conqueror first.
Though both House Bracken and House Blackwood are formidable enough on their own the best known thing about each of them is how much they absolutely loathe each other. Brackens and Blackwoods have been at one another’s throats for centuries if not millennia. Their hatred dates back to before the arrival of the Targaryens, before the arrival of the Andals, and perhaps back to the beginning of time itself.
Why Are House Bracken and House Blackwood Feuding?
Here’s the fun part of the whole thing: nobody really even knows! The Brackens swear that they were Kings of the Red Fork during the legendary Age of Heroes until they were usurped by their vassals, the Blackwoods. The Blackwoods swear the exact same thing.
Pretty much every house that can trace (or claim to trace) its line back to the prehistorical Age of Heroes likes to declare themselves kings though. Given that the Blackwoods and Brackens’ holdings are relatively close on the Red Fork, it’s more likely that the feud started with something no more complicated than a land dispute.
However unremarkable the beginnings of the feud were, however, its intensity and longevity is notorious across the realm. Countless times throughout Westerosi history, Brackens and Blackwoods have feuded and ultimately killed one another in petty disputes as seen during the Rhaenyra incident in Storm’s End.
The key word here is “petty.” Because interestingly enough, the Brackens and Blackwoods tend to agree on the big political matters in the Seven Kingdoms. Both houses were united under the banner of Aegon I Targaryen during his conquest. Later on during the events of Game of Thrones, both House Bracken and House Blackwood join Robb Stark’s cause to establish a new kingdom in the North and the Riverlands, divesting themselves from the Iron Throne once and for all.