The clan structures are kinship groups
The clan structures are kinship groups. They function, on the whole, given mating practices, within the caste structure, but they are not identical to it. For example, in a given clan there may be, though often there are not, individuals of different castes.
Many Goreans think of the clan as a kinship group within a caste. For most practical purposes they are correct. At least it seldom does much harm to regard the matter in this way. Clans, because of practical limitations on mobility, are usually associated, substantially, with a given city; the caste, on the other hand, is transmunicipal or intermunicipal.
Slave Girl of Gor, p. 360