A merit adoptive was a Chiss from a lesser family that became part of a Ruling or Great Family by adoption, based on their own skills and merits. This adoption process was called rematching.
The process to evaluate a candidate typically took two to three months, although Kivu'raw'nuru was adopted into the Mitth family much faster than that as the Mitth family Patriarch Mitth'oor'akiord intervened on Vurawn's behalf. Merit adoptives brought in via military service automatically lost the relationship when said service ended. However, those who proved themselves particularly worthy, typically by performing the Trials, could rise to Trial-born, which allowed them to keep the connection.
Certain Chiss families, such as the Mitth family, insisted that all of their merit adoptives learn the most common trade languages of the nearby parts of the Chaos, including Taarja and Minnisiat.