Early on in the first season of Star Trek: Picard, the series revealed that the chief of Starfleet Security, Commodore Oh, was a Zhat Vash spy. Oh was said to be a Vulcan, but questions about whether that was true arose when she needed sunglasses to keep the sun out of her eyes. But then she proved capable of performing a Vulcan mind-meld. It was later revealed that she was half-Vulcan and half-Romulan. Oh infiltrated Starfleet at a young age and rose up through the ranks into a position where she could orchestrate the attack on Mars that led the synth ban.
Replying to fan questions via his Instagram account, showrunner Michael Chabon revealed some new details about Commodore Oh's lineage. "Her parents were Re-unificationists, or so her Romulan mother wanted it to be believed."
This indicates that Oh is Romulan on her mother's side and Vulcan on her father's side. It also seems that her mother was a Romulan agent — either Tal Shiar or Zhat Vash — who connected with a Vulcan over the pretense of re-unification, the movement to bring the Vulcans and Romulans back together as one people, as they had been before the Vulcan forebears of the Romulans left the planet Vulcan.
The movement the reunify the Romulans and Vulcans goes back as far as the 2100s, the era of Star Trek: Enterprise, though it was under suspicious auspices at the time. The episode "Kir'Shara" revealed that the Romulan Star Empire was using a member of the Vulcan High Council to manipulate the Vulcan government and force reunification.
By the era of Star Trek: The Next Generation, Spock — by then, an ambassador — had taken up the cause fo reunification. Picard and Data were sent undercover to Romulus to search for Spock after he went missing. They discovered Spock hadn't been kidnapped but was there willingly, working with a Romulan senator towards reunification. But it turned out the Romulan agent Sela had been manipulating matters behind-the-scenes to create an opportunity for the Romulans to invade Vulcan.
It is unclear if Oh's mother sought out a Vulcan in order to breed a hybrid child capable of infiltrating Starfleet for the Romulans or if Oh's birth was unrelated to her mission. Given how long the Zhat Vash has been fighting the rise of synthetic life and how far ahead the organization thinks, the former scenario isn't out of the question.
Star Trek: Picard will return for its second season on CBS All Access.