Kitty Bennet
Pride and Prejudice Jane Austen

Poor Kitty is older than Lydia, but all she gets in the story is to be the "Kitty tag-a-long" who watches as Kitty has all the fun and gets married. These two remind me of Pippin and Merry in Lord of the Rings, a duo of "minor characters" that people tend to ignore.

Kitty Bennet
Kitty Bennet in the A&E Miniseries

Kitty Bennet
Kitty Bennet in the BBC Miniseries

Pride and Prejudice