For more than a decade, America’s most prominent gay family have lived on abc. Gay and lesbian television characters were once such a rare sight that glaad, an advocacy group, began an annual count, as if it were tracking an endangered species. Now millions tune in to “Modern Family” to see how Cam and Mitch are getting on raising their adopted daughter. Yet such families are not only the preserve of Los Angeles, where the show is set. Indeed, though data are imperfect, academic studies suggest that a greater proportion of same-sex couples have children in southern states and in the Mountain West than on the coasts.