Abstract: An example embodiment may involve estimating, from genetic data of a plurality of individuals, identity-by-descent (IBD) segments; forming, from the IBD segments, a relationship graph representing genetic linkages between the individuals; determining, by applying a stochastic block model to the relationship graph, a plurality of genetic groups, wherein each of the genetic groups is assigned a respective subset of the individuals who share a greater amount of IBD segment length with one another than with a further respective subset of the individuals who are in other of the genetic groups; and training, for each of the genetic groups, a respective classifier based on (i) input including genome-wide local ancestry proportions of the individuals and sums of IBD segments for the individuals in the respective genetic group, and (ii) associated output of assignments of the individuals to the genetic groups.