Age
At the beginning of the novel, she must be older than 15 (Lydia’s age) and younger than 20 (Lizzy’s age) with at least a little room for Mary to be older than her.
Family and Situation
Kitty is the fourth daughter of Mr. and Mrs. Bennet, making her the sister of Jane, Elizabeth, Mary, and Lydia. Presumably she’s closest to Mrs. Bennet, though Lydiadoes appear to be the favorite.
Kitty lives with her family at Longbourn House in Hertfordshire. Through her father’s estate, she will get “one thousand pounds in the four percents, which will not be [hers] till after [her] mother’s decease,” making her prospects pretty meager.
We also know that Kitty (and Lydia) frequently go into town to visit Aunt Phillips.
Other Connections
By spring in the novel, Kitty and Lydia are both spending time with Mrs. Forster, Harriet and Pen Harrington, and select officers from the regiment.
Appearance
One of the Bennet girls about whose beauty “Mr. Bingley had heard much.” Jane describes her as “slight and delicate”. Coupled with the uncontrollable coughing throughout her first scene, it may be that Kitty is a little bit sickly (of course, one might also read Jane as naive).Character
Kitty appears to be more timid and a little less quick than some of the other Bennet girls. She frequently misses the joke in her father’s quips -- she’s “disconcerted” when Mr. Bennet declares her to be one of the silliest girls in the county and doesn’t realize her father is being ironic when he threatens to ban her from leaving the house ever again. In a frustrating moment, Lizzy thinks of her as “weak-spirited, irritable, and completely under Lydia's guidance” and assumes that, as such, she will not be open to advice from anyone else. The narrator also says of Kitty and Lydia that “their minds were more vacant than their sisters’” and, as such, are less likely to sit still in the parlor, preferring to walk to Meryton and get the gossip.
Overall, it would seem that Kitty is well-intentioned but not especially self-aware. After her sisters’ marriage we’re told she spent much time with her elder sisters and that “In society so superior to what she had generally known, her improvement was great. She was not of so ungovernable a temper as Lydia; and, removed from the influence of Lydia's example, she became, by proper attention and management, less irritable, less ignorant, and less insipid.”
