Kinship estimation from ancient DNA uses the same statistical principle as modern forensic kinship analysis: the more closely related two individuals are, the larger the proportion of their autosomal DNA they share through common ancestry. Identical twins share essentially all their autosomal DNA. First-degree relatives (parent and child, or full siblings) share approximately fifty percent. Second-degree relatives (grandparent and grandchild, aunt/uncle and niece/nephew, half-siblings) share approximately twenty-five percent. Third-degree relatives (first cousins, great-grandparent and great-grandchild) share approximately twelve and a half percent.
Ancient DNA analysis of this kind requires adequate coverage of the autosomal genome — the analysis is only as reliable as the data quality and quantity allow. With low-coverage data (few DNA fragments recovered), the statistical noise in the kinship estimate is high, and only close relatives can be distinguished from unrelated individuals. With higher coverage data, more distant relationships can be detected.
The study reported that the individuals in the House of the Golden Bracelet were not closely related — specifically, that the gold bracelet adult and the child were not related at or above the threshold detectable with the coverage obtained. This is described in secondary sources as the individuals being “unrelated” or “not closely related,” language that indicates no first-, second-, or third-degree biological relationship was detected.
It is important to be precise about what this means. “Unrelated” in this context means no detectable close biological kinship — it does not mean the individuals had no shared ancestry at all, since all humans share common ancestors at various genealogical distances, and populations with shared regional origins will share more ancestry at those distances than populations from different regions. Two people from the same community in the first-century eastern Mediterranean might share considerable ancestry at genealogical distances beyond what kinship analysis can resolve, while being undetectable as close relatives.