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Olivia’s mother, Serena (Elizabeth Ashley), was a professor who became pregnant with Olivia after being sexually assaulted by a serial rapist. Serena was traumatized by the incident, and because of abortion laws at the time, kept Olivia. Serena made only one SVU appearance in the 1999 pilot (“Payback”), where she expressed grief over Olivia joining the NYPD’s sex crimes department.

Serena was an alcoholic and emotionally and physically abusive toward Olivia. In Season 20, Olivia revealed that as a teenager, she’d overheard her mom on the phone asking how anyone could love a product of rape. During one of Serena’s worst nights, she drunkenly attacked a 16-year-old Olivia, prompting her to kick her mother unconscious in self-defense. Serena resented Olivia for being a constant reminder of her trauma, but that only formed Olivia into the empathetic force of nature she is today.

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In SVU Season 2, Episode 8 (“Taken”), Olivia learned that Serena died after leaving a bar inebriated and taking a fatal fall down the stairs. Olivia was overcome with emotion, later visiting her mother’s grave.

The mystery of who assaulted Olivia’s mother remained one of SVU‘s biggest mysteries until Season 8, when Olivia ran her DNA through a kinship analysis and discovered the existence of her paternal half-brother, Simon Marsden (Michael Weston). After connecting with her brother, Olivia learned her father was Joseph Hollister, a former salesman who visited universities. Joseph leveraged his job to target female college students, Serena Benson included. After getting married and “settling down,” Joseph welcomed a son, Simon.

Olivia told Simon that their father had once tried to contact her when she was younger, but after Serena answered the phone, he hung up. Joseph’s wife eventually filed for divorce, leading Joseph to die by suicide.