Both brothers formerly worked for the Tellarite Mining Consortium while owning their own ship, the Tezra, with Skalaar as the captain and Gaavrin as the chief engineer and first officer. But they lost their ship to the Klingon Empire when Skalaar crossed into Klingon territory while hauling firesalt. Gaavrin never forgave his brother for the loss of the ship.
In 2153, Gaavrin was working on a Tellarite station as an engineer. When his brother, who was then a bounty hunter, visited him on the station, Gaavrin told him that the Klingons scrapped their former ship years before for parts. (ENT episode: "Bounty")
In 2156, the Enterprise encountered Gaavrin and Skalaar and provided them with tungsten, cobalt and magnesium to rebuild their warp coils. The brothers informed Captain Archer that they found Tellar's withdrawal from the Earth-Romulan War to be dishonorable. (ENT - The Romulan War novel: To Brave the Storm)