- You may be looking for George Kirk, father of James and George.
In 2265, Sam Kirk saw his brother off when the latter began his five-year mission of exploration in command of the USS Enterprise. Also saying farewell was Sam's wife, Aurelan and their three sons. On this occasion Sam mentioned that he wished to be transferred to the Earth Colony II research station. (TOS: "What Are Little Girls Made Of?")
Sam was a research biologist living with his family on Deneva the following year, when vessels from Ingraham B arrived carrying neural parasites. Many of the colonists, including Sam, were attacked and infiltrated by the parasites. Resisting the parasites' control was excruciatingly painful, but in early 2267, eight months after the Ingraham B vessels arrived, Aurelan managed to break the long communication blackout and get a brief distress call out to the Enterprise. By the time the ship arrived, Sam was dead; his wife died soon after. Their son, Peter, lived and was ultimately freed of the parasites. (TOS: "Operation -- Annihilate!")
The corpse of George Samuel Kirk was portrayed by William Shatner with a mustache and a different hairstyle. This was the only time that Shatner portrayed a character other than James T. Kirk (or Kirk's body being invaded or mimicked by another being).
It is unknown what happened to Sam's two unnamed children; they were not on Deneva at the time of the neural parasites' infiltration. Based on McCoy's comments to Kirk that Peter was the last surviving member of George's family, it appears they died prior to the episode.
George Samuel Kirk was to appear in 2009's Star Trek, where he would have been played by Spencer Daniels. Scenes featuring Daniels as Sam Kirk were filmed, but the character was entirely cut from the final release. The one remaining scene of Daniels playing Sam Kirk, in which Jim Kirk calls out to him as he's driving past him in their uncle's (in the final cut, their step-father's) Corvette, was altered to change the name of Daniels' character to "Johnny", apparently a friend of Jim's.
George Samuel Kirk's deleted scene from 2009's Star Trek is available on the two-disc DVD release for the film. In the scene, George runs away from home and his brother to escape the cruelty of their uncle Frank, finding it impossible to "be a Kirk" in Frank's household. He is also angered that Frank has claimed their late father's Corvette as his own. After George leaves, Jim finds the keys to the Corvette and drives off in the car. As originally conceived, Jim drove by and called out to a shocked George, who had been trying to hitchhike.
George Samuel Kirk appears in the last chapter of Star Trek: Enterprise novel Last Full Measure, set in 2238, in which an elderly Trip's first visit to the Starfleet War Memorial coincides with that of young Sam and Jimmy Kirk, rendering the quiet reflection he had hoped for an impossibility. The scene establishes George's birthdate August 12, which is also when Federation Day is celebrated. However, according to "Echoes of Yesterday" in TOS Special 3, George's birthdate was September 7, 2229, and his death took place on April 13, 2267. ("Operation – Annihilate!" originally aired on April 13, 1967)
A slightly altered version of George's deleted scene from 2009's Star Trek is found in the film's novelization. Among the scene's changes made for the book is George's revelation that Frank (who in a merger of the script and and film characters the boys' stepfather, not uncle) wants Jim to wash the Corvette, which had belonged to their late father, because he intends to sell it behind their mother's back - it is after hearing this that the decision to steal the car is made.
The alternate George appears in IDW Publishing's ongoing series, exploring events of the original series in the alternate reality, which clarifies that the boys lived with their uncle until George ran away to live with his grandfather. This later led to a rift between the brothers, James feeling that George had abandoned their mother. During their investigation of the neural parasites, Kirk and the crew discover George living underground with his family to escape the influence of the parasites after their attack on the colony, with the Enterprise subsequently devising a means to banish the parasites and cure George's family, which here is just his wife and son. At the story's conclusion, George and his family return to the colony, with George complementing his brother's success, a degree of reconciliation having been reached between the two of them.