Since the revelation that Julian Jerome is being manipulated by an unknown person calling themselves Oscar Jessup, fans have been speculating on Soaps.com's forums and Twitter that Oscar Jessup is actually a pseudonym for Julian's sister Olivia St. John, or Olivia Jerome. Olivia died on screen in 1990, the same year that Jason and Sam learned Oscar Jessup died. Jessup was a former henchman for the Jerome family.
— Lauren (@redickgirl04) November 21, 2016
Oscar Jessup. Olivia Jerome? #GH
— Lori⚡️? (@Zaggy_Stardust) December 6, 2016
Olivia St. John came to Port Charles in 1988 and was portrayed by Tonja Walker until the character's demise. Like her half-sister Ava, she was an art dealer and part of the Jerome family crime organization. She battled with her brother Julian, then played by Jason Culp, for control of their father's organization. Julian won out in the end, but enlisted his sister Olivia in his vendetta against Duke Lavery. Olivia became infatuated with and seduced Duke, but when he rejected her for Anna Devane, she became jealous and tried to kill him. However Anna became caught up in Olivia's murderous plot and in an accident lost her and Duke's unborn child. Duke would go on to fake his death to keep himself and Anna safe, but Julian thought he returned to Port Charles with plastic surgery as Jonathan Paget. He decided to put a hit out on Paget, which Olivia attempted to thwart by warning Anna. To keep his sister from ruining his plan, Julian shot and killed Olivia in 1990. Julian was believed dead from a gunshot during a struggle with Paget, only to return in 2013 under the alias Derek Wells and played by William deVry.
After departing "GH," Tonja Walker went on to play Marie Green on "Guiding Light," Grace Nancier on "Passions" and Alex Olanov on "One Life to Live."