She was born at Piʻihonua, Hilo, Hawaiʻi Island on April 7, 1839, the second daughter of Princess Kinoiki Kekaulike of Kauaʻi and High Chief Kūhiō Kalanianaʻole of Hilo. She was the granddaughter of Kaumualiʻi, the last king of the island of Kauaʻi before being ceded to the unified Hawaiian Islands governed by Kamehameha I. She was also the stepdaughter of Queen Regent Kaʻahumanu.

She was elder sister of Victoria Kinoiki Kekaulike and younger sister of Queen Kapiʻolani, who married to King Kalākaua. Some sources give her different first names; for example Esther, Abigail or even Victoria. The situation was that the three sisters rarely used their Christian names.

On March 20, 1855, she married married Hiram Kahanawai, a steward of Queen Emma. Poʻomaikelani and her husband served as in the household as retainers of Queen Emma. She was one of the trusted ladies-in-waiting for many years, but left Emma's employment to join her brother-in-law's court. The couple did not have any children of their own but adopted and raised her nephew Prince Edward Abnel Keliʻiahonui, the second son of her sister Kekaulike.

Her sister's husband became the king of Hawaiʻi in 1874 and she was granted the title of Princess and style of Her Royal Highness, in 1883 during Kalākaua's coronation. She was made Governor of Hawaiiʻi island in 1884 by her brother-in-law and was paid an annual salary of 3500 dollars per year. She also served as President of the Board of Health in 1887.

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