In a recent Letter Martinez et al.2011 have argued that the existence of extra three families is still perfectly in accord with the standard model (SM), as long as an additional Higgs doublet is also present. Here we claim that the mentioned accordan
ce can be obtained with less reliance on BSM physics like additional Higgs doublets, but benefiting from Majorana neutrinos is sufficient.
Existence of the fourth family follows from the basics of the Standard Model and the actual mass spectrum of the third family fermions. We discuss possible manifestations of the fourth SM family at existing and future colliders. The LHC and Tevatron
potentials to discover the fourth SM family have been compared. The scenario with dominance of the anomalous decay modes of the fourth family quarks has been considered in details.
