Sgt. Maj. Sam Austen
The man Kate believed for many years to be her biological father. He and Kate shared a great bond, and they shared activities with each other. For example they went hunting together, which is how Kate learned her tracking skills. He worked as a Sergeant Major in the US Army, in either the 1st, 2nd, or 3rd Battalion, 75th Ranger Regiment. He was married to Diane Janssen, Kate's mother, but the relationship broke down, most likely due to the prolonged occasions when Sam was required to travel.
- Good Scars, Evil Scars: Despite his intimidating facial scars, Sam Austen is a good man at heart who loves his daughter dearly.
- I Want My Beloved to Be Happy: Sam loved Diane, and accepted that Diane loved Wayne. Although a military man would make short work of a sleazy drunk, he wasn't going to interfere. He also didn't tell Kate the truth of her parentage because he feared she'd hurt Wayne.Kate: Why didn't you tell me that Wayne was my father? Why?Sam: I didn't tell you because I knew you'd kill him. And your mother loved him.
- The Mentor: As part of being a Parental Substitute to Kate, he also taught her many of the skills that come in handy on the Island, like tracking.
- Mercy Lead: After Kate comes to see him for one last time, Sam agrees to wait an hour before calling the authorities.
- Nice Guy: Sam is just a pleasant fellow at his core, treating everybody with respect and compassion.
- Parental Substitute: For Kate, who was under the impression that he was her father until she found out it was Wayne.
- Reasonable Authority Figure: In the army, he's fair-minded and very sympathetic to Sayid.
Tom Brennan
Kate's childhood sweetheart. Many years later, he had a baby named Connor with his wife, Rachel. He became a doctor in St. Francis Hospital in Iowa, where he scheduled a fake MRI for Kate's mother Diane Janssen so that Kate could see her one last time before she dies.
- Character Death: He's shot and killed by a police officer while helping Kate escape.
- Childhood Friends: As a child, he was Kate's best friend.
- Happily Married: Tom is married with a son, and seems pretty happy until Kate comes back.
- The Lost Lenore: He's Kate's long-lost love.
- Posthumous Character: Only appears in flashbacks, having died prior to the crash.
- Unlucky Childhood Friend: To Kate.
Wayne Janssen
Kate's biological father, though he was likely unaware of this. He beat Kate's mother Diane, was an alcoholic, and made sexual advances toward Kate (which she vehemently rebuffed). He was killed by Kate when she blew up his house in 2001.
- Abusive Parents: Kate's father was a leering drunk who beat her mother, who herself was no prize and valued her abusive husband over Kate.
- The Alcoholic: He's only ever seen drunk, albeit his only appearance is very brief.
- Alcoholic Parent: To Kate.
- Asshole Victim: Only Diane mourns his death.
- Character Death: Wayne arrives home drunk, and Kate helps him inside. She gets him into bed, takes off his shoes, and says goodnight. Then she blows up the entire house, and Wayne is obliterated.
- Domestic Abuse: He beats his wife, Diane.
- Jerkass: He's a sleazy drunken wife-beating piece of filth, so yes.
- Parental Incest: Wayne pretty clearly lusts after his daughter, Kate, who has certainly noticed his drunken leering. He's never actually physically abused her, though. It doesn't stop Edward Mars (and some fans) from speculating.Wayne: You're beautiful. Hey. Hey! I just gave you a compliment.Kate: Yeah, I heard you.Wayne: Aren't you going to take my pants off first? (grabbing her arm) You are beautiful.
- Posthumous Character: He only appears in flashbacks, having died prior to the crash.
Ray Mullen
A farmer in Australia for whom Kate worked prior to the crash of Oceanic Flight 815.
- An Arm and a Leg: Ray is the first of many characters seen with a missing limb, in this case his right arm.
- Nice Guy: Despite his betrayal of Kate (which from an outsider's perspective, seems very reasonable due to her status as a dangerous fugitive), Ray is generally a nice man willing to give Kate room and board.
Kevin Callis
A Miami-Dade police officer who married Kate. They lived together for roughly six months.
- Disposable Fiancé: For Kate. She marries him, drugs him, dumps him and he's subsequently never seen again.
- Fair Cop: Kate certainly considers him to be one.
- Good Is Boring: He's a good man, but Kate quickly grows tired with the monotonous routine of being married to him.
- Happily Married: To Kate, or so he thought. She disabuses him of that notion when she drugs him.
- Horrible Judge of Character: Kevin is a police officer...married to a notorious fugitive with a false identity.
- Nice Guy: He's only ever seen as a decent, kind person.
