A symmetry that would unify the families of quarks and leptons that are regarded as elementary particles with each family (generation) consisting of two quarks, a charged lepton, and its associated neutrino. Family symmetries have been considered as extensions of both the standard model and grand unified theories. Both continuous and discrete groups (see group theory) have been suggested as family symmetries. Currently, it appears that discrete groups that extend the standard model are the most likely family symmetries; however, this topic is still a very active subject of research.