In the short story "The Night the Bed Fell" by James Thurber, the author sets up the zany action at the end by describing the various eccentricities of the family members involved. Thurber describes these eccentricities as "crotchets." The Merriam-Webster Dictionary describes a crotchet as "a highly individual and usually eccentric opinion or preference."
The various family members, including the narrator, certainly each have their own peculiar crotchets. For instance, the grandfather disappears for days at a time and returns complaining about events that happened during the Civil War. The father goes up to sleep in the attic on a rickety bed "to be away where he could think." The narrator's brother Herman sings out loud in his sleep, and his cousin Briggs Beall keeps camphor by his bed because he is paranoid of suffocating in his sleep. To give added verisimilitude to the eccentricities of the family members he lives with, the narrator describes several other aunts not directly involved in the story who also have eccentric attitudes and behaviors.
The narrator explains these peculiar behaviors of all of these immediate family members and relatives as if they are accepted and commonplace. So yes, within the context of the story, the family members are used to each other's eccentric behavior. This becomes obvious due to the matter-of-fact style that the narrator uses in describing these crotchets. Thurber sets up the background of the peculiar characters and their eccentricities for comedic effect so that readers will be fully engaged in the slapstick events that conclude the story.