We investigate the neutrino masses and mixings extending the supersymmetric standard model (MSSM) by adding one pair of extra femilies (ESSM). We show that an SO(10) grand unified is possible to reproduce the neutrino masses and mixings consistent with the present indications with an additional SU(2)_L singlet neutrino with very light mass and which naturally has large mixing with muon neutrino. This explains the atmospheric neutrino anomaly, and the tau neutrino is provided as a candidate for the hot dark matter. Also we shortly address the bottom tau ratio problem which in the usual MSSM prohibits the the existence of the Majorana mass with its mass less than 10^<12-13> GeV. We argue that ESSM is free from the bottom tau problem. Finally we argue the U(1) assignment of our texture of the fermion and Higgs fields.