  In leptogenesis scenario, the decays of heavy Majorana neutrinos generate
lepton family asymmetries, $Y_e, Y_{\mu}$ and $Y_{\tau}$. They are sensitive to
CP violating phases in seesaw models. The time evolution of the lepton family
asymmetries are derived by solving Boltzmann equations. By taking a minimal
seesaw model, we show how each family asymmetry varies with a CP violating
phase. For instance, we find the case that the lepton asymmetry is dominated by
$Y_{\mu}$ or $Y_{\tau}$ depending on the choice of the CP violating phase. We
also find the case that the signs of lepton family asymmetries $Y_{\mu}$ and
$Y_{\tau}$ are opposite each other. Their absolute values can be larger than
the total lepton asymmetry and the baryon asymmetry may result from the
cancellation of the lepton family asymmetries.
