Within Glory City there are three major families (Manhua Variant: Name is changed to "Sovereign Families"). The City Lord is usually born from one of them. After them are the seven noble families and then the twenty aristocrat families. If a person is not a member of one of these families then they are considered a commoner. 
If a family produces a gold rank demon spiritualist, they can become an aristocrat family; if they produce a black gold rank demon spiritualist, they can become a noble family; and if they produce three black gold rank demon spiritualist or a legend rank spiritualist, they can become a major family.
A families position is largely decided by financial means and prestige. Producing strong demon spiritualists is considered essential because it results in an increase of both of these things. A strong spiritualist or fighter can join the army and draw an income relative to their rank. If a family is unable to do so, it is said to be on the decline. When this happens, the family falls in rank. This can result in a change in type, such as a major family becoming a noble family, a noble family becoming an aristocrat family, or even an aristocrat family becoming commoners. It appears that the number of each type of family is fixed, but these ranks can change greatly from one generation to another.
Note:The rank below is to give an idea of the family's power in relation to each other, with "1" being the most powerful. The ranking maybe inferred from the context in the case that it is not told outright.
Former Powerful Families: