All So'ja were linked together through the So'jan Family Clans, a system of family identification which had been set up by the Oppressors during their suppression of the so'jan people. The So'ja would take this system and use it as their own, having all so'jan families' structure based upon the clan system. (Star Trek: Pioneer)
Clan System[]
The Clan System (which was similar to a caste system), as set up by the Oppressors, broke the so'jan people up into four distinct classes: The Elite, the Upper, the Middle, and the Lower. The Elite was made up of families that the Oppressors believed to be genetically pure. The Upper, were not entirely pure, but close enough to make them superior to the other two classes. The Middle, were not pure, but were smart enough that they were able to prove themselves capable workers in the eyes of the Oppressors. The Lower was made up of all the undesirables and poor, as well as any families that carried a genetic defect.
Once the yoke of the Oppressors was thrown off many believed that the yoke of the Clan System would be thrown off as well, however, the Ru'tan, the leader of the rebellion against the Oppressors, wanted to keep it in place so that the Elite would forever be the ruling class of the so'ja. However, the family titles amongst clans were no longer a priority as they had been under the Oppressors, so that in time everyone in one clan was not, in sense, related through blood as the original concept of the system had envisioned.
Elite[]
Despite the reforms to the system, the Elite clans still maintain their genetic purity and rarely intermarry with the other clans.
Ru Clan[]
The Ru Clan was always powerful and influentially since the founding of the So'ja Kingdom, after the Oppressors were overthrown by a rebellion led by Ru'tan, who began the first So'jan King. The Ru Clan has prominent members, including Admiral Ru'mal, former head of the So'ja High Command and leader of the So'ja Resistance; as well as Senator Ru'kon. ("Grace", "In the Shadows", "Question of Loyalty", "Internal")
So Clan[]
Another elite clan, the So Clan, strategically placed themselves along side the Ru Clan so that, one day, they would assume the position as the ruling clan. Their planning succeeded, resulting in a long line of So family members presiding as King over the Greater So'jan Empire. Their reign came to an end when So'mal was overthrown by Ba'l and the Lower clans, who created the So'ja Republic. ("The Removal, Part 1", "The Boolran Eye, Part 1", "Torment and Woe")
Upper[]
Ar Clan[]
The Ar Clan was never that smart, but due to their genetic purity and strategic arranged marriages with other powerful Clans, were able to retain their Upper status. Ar'kon, was able to marry into the So Clan by marrying Sr'gi, the daughter of King So'mal, and eventually elevating to the kingship of the Greater So'jan Empire, after the coup that set up the So'ja Coalition. ("The Removal, Part 2", "Fall of the Apollo", "Torment and Woe")
Middle[]
Da Clan[]
The Da Clan had always been part of the lower class of so'jan society. Most of their family members served in the civil offices of the Greater So'jan Empire's vast bureaucratic system. However, some chose to join the military. The only Da Clan member to achieve a high status was Da'note, who became Supreme Admiral of the So'ja High Command with the Ar'kon coup. ("The Removal, Part 2")
Lower[]
Ba Clan[]
During the Kingdom era, the Ba Clan had no real power. They struggled at the bottom of the pile, along with all the rest of the Lowers. It was only through hard work and determination that one of their own, Ba'l, was able to become a senator in the Senate and eventually the leader of the So'ja Republic. ("The Removal, Part 1")