What are the motifs in The Catalogue of the Universe by Margaret Mahy?

Familial roles is a recurring idea in the story. The two principle families in Catalogue of the Universe are mirror images of each other in many ways. The Potter family, first and foremost, consists of two parents and three siblings. The only daughter, Africa, is married, has a small child, and is living away from the family home. The other two children, both teenage boys, reside in the family home. Mr. Potter, the family patriarch, has lost some of his footing in the family due to a disability that has forced him to change to a job to which he can walk (he is no longer permitted to drive the family car). At the same time, Mrs. Potter has been forced to take on a non-traditional role in the family, a role that requires her to play the role of caregiver and disciplinarian at times.