  We examine neutrino oscillations in a two Higgs doublet model (2HDM) in which
the second doublet couples only to the third generation right-handed
up-fermions, i.e., to t_R and to N_3 which is the heaviest right-handed
Majorana neutrino. The inherently large tan(beta) of this model can naturally
account for the large top mass and, based on a quark-lepton similarity ansatz,
when embedded into a seesaw mechanism it can also account for the observed
neutrino masses and mixing angles giving a very small theta_13: -0.017 <
theta_13 < 0.021 at 99% CL, and a very restrictive prediction for the
atmospheric mixing angle: 42.9(deg) < theta_atm < 45.2(deg) at 99% CL. The
large value of tan(beta) also sets the mass scale of the heaviest right-handed
Majorana neutrino N_3 and triggers successful leptogenesis through a
CP-asymmetry in the decays of the N_1 (lightest right-handed Majorana) which is
tan^2(beta) enhanced compared to the CP-asymmetry obtained in models for
leptogenesis with one Higgs doublet or in the MSSM. This enhancement allows us
to relax the lower bound on M_{N_1} and consequently also the lower bound on
the reheating temperature of the early universe.
