Here are links to some of the earliest schools of thought that layed the foundation for modern relationship science.
Humorism
http://en.wikipedia.org/wiki/Humorism
Four Temperaments
http://en.wikipedia.org/wiki/Four_Temperaments
History and the connection with temperament theory
http://en.wikipedia.org/wiki/Four_Temperaments
Temperament
http://en.wikipedia.org/wiki/Temperament