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. He became a bounty hunter to pay the impound fee, unaware that the Klingons scrapped the ship for parts.
In 2153, he kidnapped Captain Jonathan Archer for the price on his head set by the Empire in hopes to redeem himself and get his former ship back. But when he brought Archer to his brother, who was working on a Tellarite station as an engineer, Gaavrin told him that the Klingons scrapped the ship years before. (ENT episode: "Bounty")
In 2156, the Enterprise encountered Skalaar and Gaavrin 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)