Earth Colony II

From Memory Alpha, the free Star Trek reference.

Earth Colony II was a planet that hosted a research base where James T. Kirk's brother "Sam" hoped to move with his wife Aurelan and their three sons when Kirk last saw him – at the departure of the USS Enterprise on her five-year mission in 2265.

In the second year of the mission, on the planet Exo III, Captain Kirk tested Dr. Korby's android for precise knowledge of his personal history in the presence of Andrea, Nurse Chapel, and Korby: it knew that brother Sam hadn't said he would go to Colony II, but only that he hoped to go there. (TOS: "What Are Little Girls Made Of?")

It is unknown if Sam and his family ever moved to Earth Colony II prior to their posting on Deneva (sans two sons), as seen in "Operation -- Annihilate!". Since George "Sam" Kirk was a research biologist, it stands to reason that Earth Colony II had some form of indigenous life that may have attracted his interest.