The aristocrats (''hou'eiki'') of Tongan society trace their descent from the ''Tu'i Tonga'' or sacred ruler. Their status is assured regardless of titleholding. In the 18th century there were many titles (indicating control of land-and-people). Only a few of these titleholding chiefs were given the status of hereditary estateholder (''nopele'' or ''matapule ma'u tofi'a)'' by Tupou I ( in 1875, 1880, and 1882), by Tupou II (1894 and 1903), and by Salote Tupou III (1921). The place of residence for the Tu'i Tonga was Mu'a.
There are two other noble lines that impact Tongan genealogy. A change in government was done during the reign of Tu'i Tonga Kau'ulufonuafekai. He appointed his younger brother, Mo'ungamotu'a as the 1st Tu'i Ha'atakalaua, as a temportal king. Tu'i Tonga would remain the sacred or spiritual king while the Tu'i Ha'atakalaua would take care of running the kingdom overseeing the cultivation of plantations, and directing the people in bringing tribute to the Tu'i Tonga. Over time the Tu'i Tonga's power would wane and the Tu'i Ha'atakalaua's would grow.
Later the Tu'i Ha'atakalaua line would create another noble line known as the Tu'i Kanokupolu during the reign of the 6th Tu'i Ha'atakalaua Mo'ugatoga, who had married a Samoan chieftian named Tohuia from the island of Upolu, Samoa. Their son Ngata would receive the title and serve as the 1st Tu'i Kanakupolu [meaning the Heart of Upolu honoring his mother's island]. Ngata's personal god was known as Taliai Tupou and the name "Tupou" was adopted by many Tu'i Kanakupolu rulers and is now always affixed to the name of the reigning sovereign. Over time, the Tu'i Ha'atakalaua's power would wane during the time of Tu'i Ha'ataklaua Mulikiha'amea  and the Tu'i Kanakupolu's power would grow culminating in the union of all of Tonga [Ha'apai, Vava'u, and Tongatapu islands] under one ruler, King George Tupou I.