A Realistic Theory of Family Unification*

We develop an 0(18) theory of family unification consistent with all established phenomenology and cosmology. The theory makes firm predictions that will be tested soon. It implies that five new families live below 265 GeV. One of the new families is left-handed, and the other four are right-handed. The new left-handed family is lighter than its right-handed counterparts. The lightest right-handed quark should have a mass of less than 130 GeV. All the charged . aleptons should be lighter than 55 GeV; the lightest should be less than 40 GeV. The five new neutrinos have Dirac masses of less than 40 GeV, so a total of eight doublet neutrinos contribute to the width of the 2’. We study the decays of new families, and show that proton decay into etr” proceeds at an observable but acceptable rate, with a lifetime on the order of 1032*1 years.