Jaron was a Romulan living on Romulus during the 2360s. In 2368, he was a member of Spock's underground Vulcan-Romulan reunification movement.

When Jean-Luc Picard and Data visited Romulus that year to search for Spock, Jaron posed as a soldier from the Romulan military who observed the two disguised Starfleet officers as they ate soup in a Krocton Segment cafe. When Picard and Data attempted to leave the establishment, Jaron and a second soldier stopped the two, and led them to Senator Pardek, who informed them not to let his "soldiers" alarm them, as they were simply trying to get them off the streets to the underground's hidden cave system. (TNG: "Unification I")

Jaron learned about the similarities between the two races and the need for Romulans to abandon their plans of conquest and embrace logic instead. After Spock helped foil a Romulan plot to conquer Vulcan, he remained on Romulus to teach Jaron and the rest of the underground movement. (TNG: "Unification II")

Jaron was played by actor Daniel Roebuck.
His name comes the novelization. In the scripts and on the call sheets his character was referenced as "Romulan #1".
The Star Trek Customizable Card Game gives him the name Dr. Koramar. Another CCG card uses the name Jaron for a different Romulan from the episode "Future Imperfect". [1]