In a perfect sign of the peak-TV times, a single Friday brings a pair of mystery series devoted to sisters and their unique bonds, including one with (sort-of) evil twins. "Echoes" starts with promise upon which it doesn't deliver, while "Bad Sisters" -- too long, but satisfying at the end -- plays like the never-made third season of "Big Little Lies," where the really "bad" person is the abusive husband who winds up dead.
