An upcoming episode of Once Upon a Time will reveal the true identity of Zelena's (Rebecca Mader) father.

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While Once Upon a Time fans know that Zelena and Regina (Lana Parrilla) share the same mother in Cora (Rose McGowan), the former's father has been left a mystery. A Tuesday report by TVLine suggests that the identity of her father could be revealed in the same episode that McGowan returns as Young Cora.

The episode is also set to guest star Eva Bourne as Young Eva and Eric Lange as Young Prince Leopold, otherwise known as Snow White's (Ginnifer Goodwin) parents.

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"We're flashing back to Leopold's younger days to fill in more Regina backstory," Goodwin said in the TVLine report. "[Revisiting] Snow White's childhood and her parents can take us there very easily, to show how the Evil Queen's family, how those royals intertwine with my family's royal lineage."

A previous TVLine report revealed that Eva and Leopold will be in episode 18's Bleeding Through, one episode after Sunday's The Jolly Roger.

Speaking of The Jolly Roger, the episode will feature the appearance of Blackbeard (guest star Charles Mesure). The infamous pirate is set to square off with Captain Hook (Colin O'Donoghue). The Hook actor spoke about the upcoming interaction in the Tuesday report.

"Blackbeard obviously is very much a dreaded pirate, and you get to see Hook interact a little bit with him - I can't tell you how or why, because that will give away too much - but and it harks back a little bit to all the old Errol Flynn films and stuff like that," O'Donoghue said. "It's good old-fashioned, swashbuckling fun."

Once Upon a Time season 3 airs Sundays at 8 p.m. on ABC.

Watch the promo for the next episode of Once Upon a Time here:

Tags: Once Upon A Time television ABC