Defense attorney Robert Kardashian and his wife, Kris Houghton, welcome their first child, Kourtney Marie, to their posh L.A. lifestyle. Soon, the brood grows with the addition of Kim in 1980, Khloé in 1984 and Robert Jr. in 1987. In school, the sisters "clique" with classmates and future starlets Paris Hilton and Nicole Richie.
After her parents' 1989 divorce, Kourtney's family becomes even more divided when her father, Robert, defends friend O.J. Simpson following the murders of Nicole Brown Simpson and Ronald Goldman. Mom Kris – who weds Olympian Bruce Jenner in 1991 – believes the football star is guilty of killing her best friend, Nicole, but, "Kourtney and I chose to pick my dad's side because he felt like he was by himself," Kim later tells Joy Behar of the high-profile trial.
After graduating from L.A.'s Marymount High School, Kourtney enrolls at Southern Methodist University in Dallas. Two years later, she transfers to the University of Arizona in Tucson, where she leaves with a bachelor's degree in theatre arts and Hispanic studies – and a bigger bust. "I wanted to go back to school with new boobs," she said of her senior-year breast augmentation. "It was so dumb."
Just eight weeks after learning he had esophagus cancer, Robert Kardashian dies at age 59. Later, Kourtney describes to PEOPLE the impact her father had on her life: "He would always be our friend, but not too much. We would know that we could go to him and tell him everything."
Kourtney teams up with mom Kris to open the children's boutique Smooch in Calabasas, Calif. "The energy and love I put into the store truly paid off and in a weird way, the store really helped me deal with my father’s death," she writes on her blog. "I put my feelings into the store." Expanding the Kardashian fashion empire, Kourtney collaborates with her sisters Kim and Khloé for DASH, a contemporary clothing boutique, in 2006.
While childhood pal Paris Hilton makes waves with The Simple Life, Kourtney joins the cast of the unsuccessful E! reality series, Filthy Rich: Cattle Drive. Alongside privileged Hollywood offspring that includes George Foreman III, Courtenay Semel and Brittny Gastineau, Kardashian herds cattle across Montana's farmlands.
After Kim's infamous sex tape with ex Ray J surfaces, the family remains a united front, weathering the media storm together. Producer Ryan Seacrest sees TV ratings potential in the clan, and a new E! reality project called Keeping Up with the Kardashians is born. "At the heart of this series – despite the catfights and endless sarcasm – is a family that truly loves and supports one another," he tells Variety.
Though Variety dubs the sisters "talentless tarts," Kourtney's love-to-hate-him boyfriend Scott Disick becomes a guilty pleasure on their reality show. The pair, who began dating in 2006, has no qualms about airing their dirty laundry. "The only stuff they show of Kourtney and Scott is their drama," Kim says of her sister's roller-coaster show-mance, which helps catapult the series to the highest-rated show on Sunday nights among women aged 18 to 34.
After three seasons of Keeping Up with the Kardashians, Kourtney and Khloé embark on a new adventure à deux with Kourtney and Khloé Take Miami. The franchise also marks a new chapter in Kourtney's life: She splits from longtime love Disick. "I have made a ban for myself – to be single. I cannot have a boyfriend until at least a year," she tells PEOPLE.
Days before the premiere of her spin-off, Kourtney reveals some surprising news: She's pregnant with on-again love Disick's baby. "I definitely thought about it long and hard, about if I wanted to keep the baby or not," she tells PEOPLE of her agonizing decision. "God does things for a reason, and I just felt like it was the right thing that was happening in my life."
BIOGRAPHY (top to bottom): Courtesy Celebuzz.com; Vince Bucci/Getty; Michael Caulfield/WireImage; Courtesy Celebuzz.com; Bruce Gifford/FilmMagic; Courtesy E!; Seth Browarnik/Startraks; John Parra/WireImage; INF