Technically, while not spelled out as an official doctrine, Charles Taze Russell was the first to start shunning relatives. He was convinced his wife's sisters and friend was poisoning her mind with apostate ideas. He wrote letters to all of them forbidding any of them from speaking to his wife. During their divorce proceedings, it was indicated that Russell had gone around to most everyone and told them not to speak to his wife.
I am not sure when it became an official practice, but it was way earlier than 2012. I know they emphasized it heavy in the early 80s after "The Great Apostasy" and Ray Franz was df'd.