Two of the contributions applied PCA to the pedigrees in order to examine population structure and found that the top principal components reflected family structure, suggesting that the widely used PCA approach for population structure inference may not be appropriate for related samples [Thornton et al. 2013; Culverhouse et al.; 2013]. Thornton et al. [2013] proposed the R-PCA method for ancestry informative PCA with general pedigrees, and demonstrated that the top PCs from this method were highly correlated with estimated proportional ancestry from a supervised analysis with the ADMIXTURE software.
