A few explanations. Since its been over ten thousand years with scores of bastard and illegitimate children it is possible for a common dwarf be held with the original fathers of their race. Note along with Rogrim and his four brother there were an entourage of a couple hundred or so. So not all dwarves can have this background, but even as a lower class citizen they still maintain a status a little higher than the rest, but not by much. A common brewer could trace his ancestry back to the old times since they take their ancestral pride extremely seriously. But those with the most distinguished royal blood or lines of the most honorable warriors actually hold a life of luxury and titles.  The social classes go from royalty - noble elite - middle class and finally lower class. Example my character since he is of royal blood is still considered just a noble since he eighth in line for the Iron kings throne. The hierarchy is like that of any medieval society.

The Sons of Stone while they come from all walks of life are considered equal when they are called to action, the exception being is the commander who has the purest lineage followed by captains that are chosen by vote. The voted are most often the chosen captains are the spiritually enlightened or warriors of note. Most often if a father survives the service as a Son of Stone he knows that his son will inevitably chosen for this honorable service. Which results in some training onto the son. Those that don't know of their heritage or are of lower class are chosen when they're around twenty or so to further their trade skills. But this is a disguise as a five to ten year training program. As a result of this the council of stone makes sure the members are feed and families are maintained, disguised as royal decrees for their service. Which in turn results as a slightly higher status in their social group. Every 10 years a three to five month training period is mandatory to shake of any rust over the years.