  A grand unified model based on SU(5) and supersymmetry is presented. Pairs of
superfields belonging to 15 and 15* representations are newly introduced, while
gauge coupling unification is satisfied. Improper mass relations in the minimal
model between charged leptons and d-type quarks are corrected. Neutrinos have
non-vanishing masses, with large angles for generation mixings of the leptons
being compatible with the small angles of the quarks. Constraints from proton
decay are relaxed. A new source for lepton number generation in the early
universe is provided.
