  We propose the complex group theoretical Clebsch-Gordon coefficients as a
novel origin of CP violation. This is manifest in our model based on SUSY SU(5)
combined with the double tetrahedral group, T', as a family symmetry. Due to
the presence of the doublet representations in T', there exist complex CG
coefficients, leading to explicit CP violation in the model, while the Yukawa
couplings and the vacuum expectation values of the scalar fields remain real.
The tri-bimaximal neutrino mixing matrix arises from the CG coefficients of T'.
In addition to the prediction for theta_{13} ~ (1/ (3\sqrt{2}) theta_{c}, the
model gives rise to a sum rule, tan^{2} theta_{sol} ~ tan^{2} theta_{sol, TBM}}
+ (1/2) theta_{c} cos(delta_{lep}), which is a consequence of the
Georgi-Jarlskog relations in the charged fermion sector. The predicted leptonic
Dirac CP phase, delta_{lep}, gives the correct value of the solar mixing angle,
and the predicted CP violation measures in the quark sector are consistent with
the current experimental data. Since the Dirac CP phase is the only
non-vanishing phase predicted in the lepton sector, there is a connection
between leptogenesis and low energy leptonic CP violating processes in our
model.
