We introduce a case of disputed parentage with 2 presumptive related fathers, although using multiple genetic systems, neither of the 2 fathers may be excluded. Nineteen autosomal short tandem repeat typing and 12 X-chromosome markers could not clarify the case. We can conclude that forensic autosomic short tandem repeats included in commercial kits are not sufficient to definitively discriminate parent-offspring with related putative fathers in forensic laboratories, and supplementary investigations should be available for selected cases.