King Kong is a gigantic gorilla-like primate that lives on Skull Island. In one of the versions of the story, Kong's species are probably not related to gorillas, though, and are more likely to be related to the extinct ape Gigantopithecus. They probably grew in size to be protected from predatory dinosaurs, such as Venatosaurus or Vastatosaurus rex. As the result of being killed by huge predators, storms, and earthquakes, the species has been declining leaving Kong the last of his kind.
In the 1933 film, The only individuals left were King Kong and his son, Kiko. While King Kong was shot off the Empire State Building in New York, Kiko was killed due to the flooding of Skull Island.