Actually they are more clan related! For example, The Yuki clan used Hyouton or the Ice Style. The Hyuga have the Byakugan, and the Uchiha the Sharingan.
It could also mean that people are capable of teaching a KKG to those who have the right affinities to use it...though it would be an extremely low number of people.
It just happens that in Naruto, usually one style is given to an individual in order to make them appear unique...For example: Haku being the only Yuki clan member, Kimmimaru being the last of the Kagura (I think) clan.