  Recent measurements of the neutrino solar mixing angle and the Cabibbo angle
satisfy the empirical relation theta_{sol} + theta_{C} ~ 45^{o}. This relation
suggests the existence of a correlation between the mixing matrices of leptons
and quarks, the so called quark-lepton complementarity. Here, we examine the
possibility that this correlation originates in the strong hierarchy in the
mass spectra of quarks and charged leptons, and the seesaw mechanism that gives
mass to the Majorana neutrinos. In a unified treatment of quarks and leptons in
which the mass matrices of all fermions have a similar Fritzsch texture, we
calculate the mixing matrices V_{CKM} and U_{MNSP} as functions of quark and
lepton masses and only two free parameters, in very good agreement with the
latest experimental values on masses and mixings. Three essential ingredients
to explain the quark-lepton complementarity relation are identified: the strong
hierarchy in the mass spectra of quarks and charged leptons, the normal seesaw
mechanism and the assumption of maximal CP violation in the lepton sector.
