Can brothers share the same STR profile?

This report demonstrates the limits of DNA identification when siblings are involved. The Israeli DNA database routinely amplifies suspects samples using the PowerPlex(®) ESI16 system (Promega). While uploading a series of suspects into the database software, we found an unusual high number of shared alleles between two suspects 31 out of 32 alleles. Verification of their demographic data identified them as brothers. After confirmation of their paternity affiliation using the AmpFlSTR(®)YFiler™ (Applied Biosystems), we used two other multiplexes kits to improve the differentiation rate. The PowerPlex(®) ESX17 System (Promega) added one locus, SE33, who exhibits four different alleles. The second kit, the AmpFlSTR(®)MiniFiler™ (Applied Biosystems) added three more loci. Only one allele difference was found. In order to increase the discrimination power between related and unrelated individuals, we recommend that the DNA laboratories consider using a larger multiplex typing kit in cases like the one informed here.