Kate Austen is one of the main protagonists of Lost, and thus his family is central to the series and its stories.
- Kate Austen - A fugitive on the run for killing her father who was caught in Australia and taken back to Los Angeles, but the plane she was on crashed.
- Wayne Janssen - Kate's father (who she believed to be her stepfather) and she killed him.
- Sam Austen - Kate's stepfather who she believed to be her father.
- Kevin Callis - Kate's estranged husband who she married under the alias of "Monica".
- Aaron Littleton - Claire Littleton's son, whom Kate cared for, for 3 years when Claire went missing.
- Mr. Callis - Kate's former father in law.
- Suzanne Callis - Kate's former father in law.
- Kevin's brothers - Kate's three unnamed, former brothers-in-law.
- Jack Shephard - Kate's ex-fiance who she met on The Island.
- James Ford - Kate's past romance who she met on The Island.
Note: Jack's family, Claire's family and Sawyer's family intertwine with Kate's.
|Portrayed by Evangeline Lilly, Emily Rae Argenti and Skye McCole Bartusiak|
|Shared and non-centric flashes|