Tuʻi Tonga Fefine/en

In the beginning of the 17th century the current Tongan ranking system became well established. This was probably due to the invasion of ʻUluakimata I with his 500 ʻUvean warriors to claim the title of the Tuʻi Tonga a century or so before. It was a long time of social changes, but Tongan culture changed from something completely different then, to the structure it still has nowadays. 

In the new system the rank of the sisters of the Tuʻi Tonga was higher than of the king himself, especially the rank of his his oldest sister. She became known as the Tuʻi Tonga Fefine (female Tonga king; but she was not his wife). (These 'real' Tuʻi Tonga Fefine are different from the occasional named Tuʻi Tonga Fefine during earlier generations.) Sinaitakalaʻilangileka was the first Tuʻi Tonga Fefine.

Evidentlty the Tuʻi Tonga Fefine was not really a dynasty with a daughter succeeding on her mother's death. Their existence followed the Tuʻi Tonga, so there could be one, or none, or perhaps two Tuʻi Tonga Fefine at any particular time.

A Tuʻi Tonga Fefine had to marry a foreigner, because her children would be higher ranking than the Tuʻi Tonga himself. But as non-Tongans these children would not eligible to compete for Tongan kingship, whatever high the rank, leaving teh Tuʻi Tonga alone. Or so was the official belief and explanation. With them started the Fale Fisi, of which the Tuʻilakepa and the Tuʻihaʻateiho were the leading lineages, and also started the institution of the Tamahā, the oldest daughter of the Tuʻi Tonga Fefine.
D.V. Burley; Sacred child and sacred place; Polynesian paradox, USP 2005; ISBN 982-02-0371-6
https://web.archive.org/web/20071121233019/http://findarticles.com/p/articles/mi_m2375/is_n2_v32/ai_20554487/pg_7