Kay is the daughter of the two main characters in the show. She is introduced in season 4 episode 3 when her mother Selina gives birth to her. All of season 4, she's just a baby. However, in season 5 she's a teenager. She is kind, caring, polite (in appropriate situations), badass, brave but curious. In season 4, when she was a baby, things happened, terrible things that the parents had to go through to protect their daughter. Throughout season 5, she asks questions about it but no one gives her a proper (They don't want to talk about it).  She can take well care of herself, she can fight the dead no bother but she never experienced the threat of people yet. When she gets that, her point of view on new people will be different. She is around for a long time in the show. There are 8 seasons left. I won't say if she survives or not, that's one of the main secrets of the show. Throughout the show you see her learning more about the outside world, the danger of people and her parents past.