Karly’s first appearance is as a ten year old girl born in early 21st century Britian. Her parents are Robert and Patricia Jacobs. She has no siblings. Her family life can be considered quite dysfunctional. She was not a wanted child and her parents have let her know this fact, though admittedly they have not thrown it in her face. In fact, her parents aren’t actively mean to her. They are just thoroughly disinterested, her presence a distraction to their own lives.
Karly’s parents are divorced, and there is hostility between them. Mostly is seems to be who will get stuck taking care of Karly. The courts have mandated 50/50 custody, and Karly shifts between the two parents every week. Usually, each parent will find a sitter to take care of her, take her along to work (when she isn’t in school) where she is placed somewhere out of the way, or even left home alone.
Despite all this, Karly does love her parents, though she accepts that her parents do not love her. She is obedient as much as a ten year old girl can be, but being love-starved, she attaches very quickly to anyone who shows even a glimmer of interest in her.
When the Doctor arrives in her life, she gravitates toward him and is eager to share in whatever adventure he is involved in.