Our body is in part comprised of cells, most of which contain the DNA molecule, which gives us our uniqueness as individuals. Certain parts of this molecule have been shown to contain specific regions that vary considerably between people who are not related and conversely, that exhibit a high degree of sharing between individuals who are related. These regions are referred to as ‘markers’ or ‘loci’ (singular: locus). Variant forms of these DNA markers are called ‘alleles’. There are two alleles found at each locus. We use 23 or so markers to determine if people are related to each other or not. This is robust science, which has been tested over thousands of cases, both for human identity testing and forensic purposes.