allows for the estimation of identity-by-state between individuals in a dataset. Identity-by-state can be used as a proxy for identity-by-descent, or the degree of allele sharing due to common ancestry, a common measure of relatedness. Obviously, in samples where families are ascertained, it is expected that relatives will be present in the dataset and appropriate methods for accounting for dependence between subjects will be used in subsequent association testing. However, when unexpected relatedness among individuals is discovered (e.g., IBD/IBS > .1875, or midway between the expected genetic similarity of second- and third-degree relatives; Anderson et al., 2010) it is the usual practice to randomly delete all but one of the correlated observations.
