Final answer:
When genealogical connections cannot be documented among the Nuer tribe, the concept that represents this is a lineage within the larger kinship structure.
Step-by-step explanation:
In the context of the Nuer tribe, when genealogical connections cannot be documented, the concept that best represents this is a lineage. Lineages are groups of people who trace their descent from a common great-grandfather, and they are encompassed by larger groups called clans. In disputes between lineages, individuals can recruit allies from the larger kin groups to settle conflicts.