Firstly... let's not pretend that underwear shop has anything that would fit any of them.
Every single member of that family besides the youngest sister would need custom-made bras... and frankly I doubt the shop has panties to fit most of them either. They're big girls, and underwear for big girls is not easily nor cheaply obtained, unfortunately.
Secondly... why do they keep forgetting the aunt?
She is the one with the glasses, so it stands to reason I wish she'd show up more... though she seems to be the least shown of the family members besides the elusive father.