In the Star Trek fictional universe, George Samuel "Sam" Kirk was the older brother of Enterprise Captain James T. Kirk.

Sam was married to Aurelan Kirk, and they had a son named Peter. In the 2260's Sam and his family went to Deneva. George maintained a lab on the planet.

In 2267, the USS Enterprise came to Deneva to investigate massive insanity. Upon arrival they were unable to establish radio communications. Captain Kirk led a team to the planet surface. When arriving at Sam's residence, Kirk and the Enterprise crew found Sam dead, Peter unconscious, and Aurelan in an extremely agitated state. Aurelan and Peter were taken up to the Enterprise. Aurelan later died on board the Enterprise. The crew determined that neural parasites had invaded the colony. The Enterprise was able to destroy the neural parasites, and stop their invasion of the galaxy.