Previous analyses of alleged siblings have calculated the conditional probability of a test sibling's genotype given a reference sibling's genotype; however, more genetic information is available when two or more reference siblings are tested. Based on the root concept of identity by descent (IBD), we present a sibship method of parental genotype reconstruction (PGR) that can use any number of reference sibs. Nine PGR patterns, along with their respective IBD proportions of full-sibs and half-sibs, were identified and used to calculate joint sibship probabilities and likelihood ratio formulas. In addition, a correction PGR was developed for situations involving the same genotype repeating in the reference sibs. The method is simple and can be applied to any number of alleged full or half-siblings.
Keywords: forensic genetics; forensic science; multiple siblings; parental genotype reconstruction; sibling index; sibship test.
© 2016 American Academy of Forensic Sciences.