A mother, a Chiss female, bore Mitth'ras'safis. Prior to her rematching into the Mitth family, she and her husband were members of a very minor family. One week before their son's birth, her husband lost his life while saving Mitth Patriarch Mitth'oor'akiord from an assassination attempt. Subsequently, the Patriarch invited the widow to the Mitth family homestead on Csilla and proposed matching her to the Mitth as a ranking distant, the highest rank a commoner could receive. She accepted this proposal. Given that her son had already been born, he should have been a ranking distant as well, but the Patriarch changed the rematching date to occur after the assassination but before Thrass's birth, resulting in Thrass being recorded as a Mitth cousin in the family records.
During a visit to his mother in 37 BBY, Thrass was unexpectedly summoned to Patriarch Thooraki's office. He was given the mission to prevent the Stybla family from abducting one of the Mitth merit adoptives, a young lieutenant in the Expansionary Defense Fleet named Mitth'raw'nuru. Over the years, Thrass and Thrawn developed a close bond, with Thrass eventually considering him his brother. As a demonstration of his trust, Thrass confided in Thrawn the story of how he and his mother came to be part of the Mitth family.