Hereditary rulers didn't all rise from a stratified society. They created the strata. Prince, princess, Duke, duchess etc. Etc etc. The strata was always their family and friends. Strata like that would not exist without them.
History has been filled with usurpers to the throne. Who have then gone on to set up their own dynasties etc. it's actually quite normal. And in the process they turned up the strata. Replacing it with people, loyal to them. Because the strata itself is meaningless and is just meant as a positive feedback mechanism.