The Tu'i Ha'atakalaua dynasty is believed to have begun in the late 15th century when Tu'i Tonga Kau'ulufonua Fekai (the 24th Tu'i Tonga) gave his younger brother, Mo'unga'motu'a, the title of Tu'i Ha'atakalaua (their fathers name). The primary role of the Tu'i Ha'atakalaua was to act as an executor for the Tu'i Tonga's functions and duties, as he remained above the day-to-day running of his land and people. The first Tu'i Ha'atakalaua also played an important role in the protection of his brother, as their father had been assassinated and there was concerns that the same might happen to the Tu'i Tonga Kau'ulufonua Fekai.
The Tu'i Tonga, Tu'i Ha'atakalaua and their followers lived on the eastern side of Tongatapu in an area known as Fonuamotu – today, this is the area around Mu'a. The Tu'i Tonga resided in a region of Fonuamotu known as Kauhala'uta (roadside above), and the Tu'i Ha'atakalaua in a region called Kauhalalalo (roadside below).
In the early 17th century, the sixth Tu'i Ha'atakalaua, Mo'unga'otonga, gave his first son Ngata the title of Tu'i Kanokupolu. As was in the case of the establishment of the Tu'i Ha'atakalaua title, the Tu'i Kanokupolu title was also established to assist and protect both the Tu'i Tonga and Tu'i Ha'atakalaua. The Tu'i Kanokupolu was based in Kanukupolu village on the western side of Tongatapu. This was a strategic move by the Tu'i Ha'atakalaua Mo'ung'otonga to ensure that the western as well as the eastern sides of Tongatapu were protected for the Tu'i Tonga in case there were any ideas of rebellion by the people.
The establishment of the Tu'i Kanokupolu title was an important event, as the Tu'i Kanokupolu became the third and now paramount dynastic line of Kings in Tonga.
Unlike the Tu'i Tonga and Tu'i Kanokupolu dynasties, the title of Tu'i Ha'atakalaua does not pass from father to son (although this occurred in most cases as shown in the below dynasty line). The title is passed onto one individual person and when that person dies, the title is then bestowed on another by the falefa (spokesperson). The new Tu'i Ha'atakalaua was often a man of high regard and character and one who came from a good family. The last of the Tu'i Ha'atakalaua's died in the 18th century.
In 1875, King Siaosi (Taufa'ahau) Tupou I re-established the title of 'Ulu (Head) Ha'atakalaua to Tungi, the grandson of Mulikiha'amea, the last Tu'i Ha'atakalaua. It was believed that this decision was made for strategic reasons. Tungi was a well respected Noble and had a large amount of land and supporters around Takakamotonga and Fua'amotu on the western side of Tongatapu. In order to secure his support for the newly established Tupou royal line, King Siaosi Tupou I offered Tungi the title of his grandfather.
In 1917, Tungi Mailefihi (Tungi's grandson) married Princess Salote Mafile'o Pilolevu (daughter of King Siaosi Tupou II). Following King Siaosi Tupou II's death in 1918, the Princess became HRH Queen Salote Mafile'o Pilolevi Tupou III. The first born child of Queen Salote and Tungi Mailefihi was Crown Prince Siaosi Taufa'ahau Tupoulahi (1918 – 2006). In 1936 Crown Prince Taufa'ahau was bestowed with a Noble title and took the name Crown Prince Tupou To'a. Then again in 1945, Crown Prince Tupou To'a received the Tungi title and became known as Crown Prince Tungi. Following Queen Salote's death in 1965, Crown Prince Tungi was coronated as HRH King Taufa'ahau Tupou IV. He also kept the Tungi title (head of the Ha'atakalaua dynasty).
In 2006, HRH King Taufa'ahau Tupou IV died and the Tungi title still remains to be given. His son, HRH King Siaosi Tupou V has not taken on the Tungi title, but rather, will bestow it on a close family member within the next few years.
Tu'i Ha'atakalaua Line
1. Mo'ungamotu'a (younger brother of Tu'i Tonga Kau'ulufonua) – approximately 1470 A.D.
2. Tanekitonga (son of Mo'ungamotu'a)
3. Va'e'omatoka (son of Tanekitonga)
5. Vakalahimohe'uli (son of Siulangopo)
6. Moungatonga (son of Vakalahimohe'uli, brother of Ngata – the first Tu'i Kanokupolu)
7. Fotofili (son of Moungatonga)
8. Vaea (son of Fotofili)
9. Moeakiola (son of Vaea)
10. Tatafu (son of Fotofili)
11. Kafoamotalau (son of Vaea)
12. Tu'inukulave (son of Kafoamotalau)
13. Silivakifanga (son of Tu'inukulave)
15. Maealiuaki (abdicated from the Tu'i Kanokupolu to become a Tu'i Ha'atakalaua)