Joseph Samuel T'Kol T'Lan Kirk was the child of James T. Kirk and Teilani of Chal. Joseph was born in 2375, a month premature, after his mother nearly died from a poisoning. Joseph never came to know his mother, however, since she was killed at Halkan during a rescue operation aboard the USS Pathfinder several weeks after his birth. He was subsequently raised until the time of his apparent death by his widowed father, James T. Kirk.

Being the child of Kirk and Teilani, Joseph was a hybrid of Human, Romulan, and Klingon DNA. This mix ultimately proved to be a near- match with the genetic profile of Professor Richard Galen's ancestral species. Because of his unusual genetic profile, Joseph was a hermaphrodite; however, despite this, Joseph was always treated as a boy by his own choice.

Joseph seemingly sacrificed himself to save his father and the Milky Way Galaxy from becoming overrun by the Totality in 2381 at the age of 6. He transformed into the pure energy of the galactic barrier and consumed the agent sent by the Totality to assimilate the life within the Milky Way into the dark matter realm. His body was never recovered, but it is accepted that he is forever gone. James T. Kirk added a new gravestone on the property of his cabin on Chal for Joseph next to the one for Teilani. (TOS novels: Preserver, Captain's Blood, Captain's Peril, Captain's Glory)