All of the Noble Houses of Westeros celebrate their own Lore- stories of heroic deeds by ancestors whose names are well-known not only by their descendants and vassals to their House but by nearly all Great and Noble Families throughout Westeros, as well as the smallfolk of The Realm. That is to say, all Noble Houses celebrate their Lore except House Mormont of the exceptionally boring Bear Island; a House which seems to have no Lore whatsoever.
House Mormont is an old house of The North, though not an ancient house like The Starks. However, as of the events of ASoIaF, The Mormonts are one of the principal families that are sworn to House Stark. Perhaps even more so with events that have transpired during ASoIaF if we base our assumptions on the yet-to-be-published-yet-already-adapted-material that takes place during HBO's Game of Thrones.