Allele frequencies for the 12 short tandem repeat loci of the Investigator Argus X-12 kit were obtained from 514 unrelated Taiwanese individuals (327 males and 187 females). Hardy-Weinberg equilibrium tests with samples demonstrated no significant deviation from expected values for all 12 loci (p > 0.05). The linkage disequilibrium for the 12 loci in the female samples was identical to what was observed in other Han Chinese populations, with only the DXS10103 and DXS10101 loci showing significant linkage disequilibrium after corrected by Bonferroni's correction for multiple testing (p < 0.05/66). No significant differences were observed by population pairwise genetic distance analysis between Taiwanese and other Han Chinese populations. When compared with other Asian, European, and African populations, however, significant differences were observed at more than one locus. The combined mean exclusion chance was 0.99999 in duo cases and 0.99999999 in trio cases. This study used mathematical logic inferred likelihood ratio calculation formulas for full-sister, half-sister from the same father, and paternal grandmother-granddaughter relationships. The results for these three real familial cases suggest that these 12 short tandem repeat loci may appropriate for forensic relationship testing.