House Umber appears to be the most northern of the houses of Winterfell, with Last Hearth beyond the Last River and not very far from Eastwatch-by-the-Sea on the Bay of Seals. Jon Umber, called the Greatjon, is its lord, with his son and heir, also Jon, called the Smalljon. Lord Umber’s uncles, Mors Crowfood and Hother Whoresbane, aid him in ruling Last Hearth.
The Greatjon disliked the idea of following Robb Stark to war, but after losing a pair of fingers to Grey Wind he proclaimed himself Robb’s most loyal man. He was the first to proclaim Robb King of the North and accompanied him into the westerlands, where they have successfully raided in the Lannister lands. The Smalljon is one of Robb’s sworn battle companions.
While away, the Greatjon’s unsavory uncles Mors Crowfood and Hother Whoresbane have held Last Hearth. While Ser Rodrik later called the Umbers down to join him in laying siege to the Greyjoy-held Winterfell, they did not appear, the reason unknown. At the Red Wedding, the Smalljon was murdered and the Greatjon was put in chains. Hother Whoresbane proceeds to take the old men the Greatjon left behind and form a host to join with Roose Bolton, while Mors Crowfood takes the green boys the Greatjon left to form a host to join Stannis. Hother is inside Winterfell while Mors is outside of it when the great snowstorm falls. Mors proceeds to capture the escaped Theon Greyjoy and Jeyne Poole (believed to be Arya Stark) and sees them delivered to Stannis.