Ancestors
In 2364, Captain Jean-Luc Picard speculated (correctly) that the ancestors of the Brekkians living as of that year discovered the narcotic properties of felicium and cured themselves of their addiction without sharing this fact with the Ornarans. (TNG: "Symbiosis")
Female
During the Breen occupation of Brekka in 2381, this female was the only Brekkian seen on the planet's surface. She was approached by Commander Jack Ransom of the USS Cerritos, who attempted to console her. She nervously tried to warn him to leave, prompting Ransom to attempt to console her, and ask where the other inhabitants of the planet were. Before she could tell him, however, she was disintegrated by a blast from a Breen disruptor. (LD: "Trusted Sources")
Langor's grandfather
According to Langor, in her grandfather's day, the amount of felicium she and Sobi were hauling would have filled five rooms the size of the USS Enterprise-D's cargo bay. (TNG: "Symbiosis")