Katherine Jo Henderson was born July 1, 1999, in Oxford, Mississippi to Philip and Michelle Henderson. Katie, as she was called, had an older sister, Rebecca, and a much younger brother, Vincent.
Philip was a brain surgeon and Chairman of the Neurosurgery Department at Baptist Memorial Hospital in Oxford. Michelle was a pediatrician at Children's Clinic of Oxford.
Katie was a happy child, and although her parents were very busy with “important work” as they told her, she was content and got plenty of attention from them. Katie and her sister were cared for by a sweet, elderly British woman who they called "Aunt Clara."
The year before Vincent was born, Aunt Clara’s health began to fail, and she returned to England to be with her family. The Hendersons' remaining household staff took responsibility to make sure Rebecca and Katie were dropped off at and picked up from school.
In Spring 2010, Michelle was put on bed rest due to complications during her pregnancy with Vincent. When Vincent was born, Michelle decided that she would take at least one year off before returning to work.
At first, Katie was thrilled to have her mom at home, but as the weeks went by, Katie was made responsible for more and more of the housework and infant care. She quickly grew tired of cleaning up and caring for both Vincent and her mother, and Katie especially resisted being put in the role of Vincent’s primary caregiver.
Even though Katie was an average student and didn’t love school, she claimed she was pursuing a path in pre-med. She was allowed to stay late after school to study or to get tutoring, thereby avoiding her enormous household responsibilities.
Michelle eventually went back to work and hired a nanny to care for Vincent. Since Katie maintained good grades, her scheme of studying and getting tutored after school went unchallenged.
Katie kept her same "study habits," but instead of staying after school, she would hang out with her best friend, Alyx Byrns. From the time Katie and Alyx met in grade school, they were inseparable.
The girls shared many interests. As they got older, those interests consisted mainly of partying, boys, and pulling elaborate, well-constructed pranks on people.