NBC is putting more ethnic diversity in its new and returning series, partly in response to criticism of the major broadcast networks for a nearly all-white slate of new fall shows. The network said it is working with actor-writer Keenen Ivory Wayans and producer Yvette Lee Bowser (“Living Single”) to develop a pair of sitcoms that will feature black characters. Wayans’s show was described as “Not the Bradys,” featuring an interracial marriage and the resulting merged family. Several planned cast additions involve minority actors: Sherri Shepherd on “Suddenly Susan”; Jesse L. Martin on “Law & Order” and Michelle Hurd on its spin-off, “Law & Order: Special Victims Unit”; Darryl Theirse on “Jesse” and Michael Michele and Ming-Na Wen on “ER.”