Roger Korby was born in the 2210s, and quickly rose to be an eminent scientist in the Federation. During his scientific career, Korby conducted many archaeological expeditions to planets all over the Alpha and Beta Quadrants. In the 2240s, Korby was part of a team led by Dr. Phillip Boyce that was attempting to cure Dezzla's disease on Argelius. (TOS short story: "Snake Pit!"; TOS novel: The Children of Kings)
During an archaeological expedition to Vestalan in 2259, Korby was able to study the remains of the long-lost Hualan civilization, and forwarded the Federation's knowledge of dead cultures. Accompanying him on this expedition was the research biologist, Christine Chapel. Korby and Chapel became very close during the expedition, and soon after the two were engaged to be married. (TOS short story: "Snake Pit!")
In 2261, Dr. Korby and his associate, Dr. Aaron Brown were conducting a survey of the civilization on Exo III, when their ship crashed into the wilderness. Dr. Brown was killed instantly, but Korby survived long enough to be found by an android named Ruk. Korby begged Ruk to save him, and Ruk obliged by creating an android duplicate of Korby. The human Korby died shortly thereafter. (TNG novel: Immortal Coil)
The android Korby went on to create a duplicate of Dr. Brown and a female companion named Andrea. In 2266, the USS Enterprise arrived at Exo III to ascertain the location of Korby's expedition, along with Christine Chapel. After an attempt to take over the Enterprise to spread the androids across the Federation, the Korby android was destroyed. James T. Kirk saw for himself how an android dangerously mimmicked his behavior. And having seen another android, altogether replacing a human, Kirk decided that the Roger Korby they sought was, "never here." (TOS episode: "What Are Little Girls Made Of?")
For the purposes of this wiki, this article describes both Roger Korby and his android duplicate. The ending of the episode called into question the efficacy of Korby's process transferring mentality, which makes it unclear if the android was actually the conscious mind of Korby, or a separate being programmed to emulate Korby, in which case the android would be an entirely separate entity.