At the beginning and the end of Alice's Adventures in Wonderland, Alice is strongly contrasted with her unnamed older sister. Alice's sister is grown-up enough to sit quietly on the riverbank reading a book "without pictures or conversations," while Alice picks flowers and makes a daisy-chain. Alice's imagination is much more active than her sister's, which seems to suggest that creativity is lost with age. Yet when Alice tells her sister about her adventures, her sister appreciates them and starts to incorporate them into her own daydreams – which is, perhaps, what the adult reader of the book is supposed to do.
Mabel, a dull-witted and poor child, is one of several unseen characters developed as foils for Alice. Mabel is slow at her lessons and her family isn't very well off – Alice says they live in a "poky little house" and that Mabel has hardly any toys to play with. When Alice starts to have trouble reciting her lessons, she worries that she may have turned into Mabel.
Lily, the White Queen's young daughter, is meant to be one of the White Pawns in the chess game that structures Through the Looking-Glass. However, as the Red Queen explains, Lily is "too young to play," and so Alice can take her place. Although Alice is young and naive, Lily is even more so, suggesting that Alice herself represents the perfect balance between youth and maturity.