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Tiberius. This was the name of his paternal grandfather, according to the film Star Trek (2009).  It's also interesting that Kirk's middle name was no offical until 1991, when it was spoken onscreen in Star Trek VI: The Undiscovered Country. Click on the hyperlink for more information.   TrekFan1984 Ends (talk) 22:32, September 20, 2017 (UTC)