What happens to Mary and Kitty Bennet is Pride and Prejudice?

Answer 1

At the end of the book, Kitty moves to Pemberley, where she lives with Lizzy, Darcy and Georgiana. There, she improves greatly from exposure to company better than Lydia's.

Mary stays at home with her mother, the only one of the daughters to do so.

Answer 2

Mary remains single and lives a quiet life focused on intellectual pursuits, while Kitty eventually matures and improves her character under the guidance of her older sisters. Both sisters find their place within the family and society by the end of the novel.