What does it mean when a paternity test reveals the parents share eighteen out of 40 alleles and are identical matches on five of twenty genetic markers?

When a paternity test reveals that the parents share eighteen out of 40 alleles and are identical matches on five of twenty genetic markers, it suggests a partial genetic relationship but does not confirm paternity. Typically, a child inherits half of their alleles from each biological parent, so a lower than expected number of shared alleles may indicate that the tested individual is not the biological parent. The results can also suggest a more distant familial relationship, such as that of a relative. Further testing or additional context may be needed for a definitive conclusion.