Squadron

A "Squadron" within the Celestial Empire is a group of non-related Tseibajeen that live together as a sort of family unit. All Tseibajeen (except for the nobility class) grow up as a member of a Squadron. Members within a Squadron are assigned to live and grow up together starting at the age of 2. Group members are almost always approximately the same age. The standard size of a Squadron is 4, but in the event of a death, Squadrons can be combined such that their numbers are 6 and occasionally 7 in total. Group members are selected based on whether sorters believe they will work well together when they grow up.
Usually, there are an equal number of males and females within a Squadron, and special care is taken to ensure that there are no blood relationships between members of a Squadron. Because of this, it isn't forbidden, and is in fact expected, for males and females within a Squadron to produce offspring together when they are old enough. However, this is only permitted to groups that are actively serving their mandatory military service, or those who have completed their service to a degree that is satisfactory to the Empire. The purpose of this rule is to bolster the numbers of the military, ensure the genetics of the Tseibajeen race remain strong, while the weak die out.
Fay, Soren, Saito and Kallio  are the four members of a @Squadron.