Diane Janssen (formerly Diane Austen) is the mother of Kate Austen.
Before the crash
Diane became pregnant with Kate by a man named Wayne (possibly while she was still married to Sam Austen). Kate grew up believing that Sam was her biological father. Eventually, Diane returned to Wayne, despite the physical abuse he inflicted upon her. Wayne, who was an alcoholic, made repeated advances toward Kate, who was still unaware of the "true" identity of her father.
While making a photo album of all of Sam's war pictures, the dates caught Kate's eye. The photos showed Sam at war, dated up until four months before Kate was born. Kate then understood the truth - Wayne was her real father, as there was no way Sam had contact with Diane around the time of Kate's conception.
Disgusted at how he was ruining her mother's life, Kate blew up Wayne's house while he was still inside. Before fleeing, Kate consulted Diane about what she had done. Diane, fueled by the fact that her own daughter had just killed the man she loved, gave Kate up to the police. ("What Kate Did")
Kate needed to know why Diane had turned her in. With Cassidy's help, Kate confronted her mother. Diane told her, "you can't help who you love, Katherine, and for good or bad I loved him." When Kate tried to defend herself, Diane retorted that Kate killed Wayne for herself, not for Diane. She then told Kate that she would not turn her in, but if Kate came back, Diane would yell for help. A devastated Kate left. Kate told Cassidy she could not forgive her mother. ("Left Behind")
Diane eventually developed cancer. Through a chain of events, Kate was able to visit her mother, who was believed to be dying, in the hospital. Diane, who was apparently unaware of the setup, was taken by surprise when her daughter showed up and began to scream for help, just as she had warned she would. A doctor rushed in to see what was going on, but Kate ran for the door just in time. ("Born to Run")
After the rescue of the Oceanic 6
Diane's doctors told her that she had only six months to live, but she managed to survive for another 4 years, long enough to see Kate return from the island and stand trial for Wayne's murder. Diane was meant to be the prosecution's chief witness, but the experience of first believing Kate was dead and then being told after Kate's return that she had a grandchild caused Diane to have second thoughts. Diane, who had become bound to a wheelchair and an oxygen tank by her illness, asked Kate to let her see Aaron in exchange for a promise not to testify. Kate refused, but Diane still ended up not taking the stand. According to Melissa Dunbrook, this was due to medical reasons. ("Eggtown")
- Last name may be a reference to the TV show The Fugitive, which starred David Janssen.
- For fan theories about these unanswered questions, see: Diane Janssen/Theories
- Is she aware that Kate discovered that Wayne is her biological father? Is this what she meant when she told Kate that she killed Wayne for herself, and not for her?