He became the only Native Hawaiian to be ordained a deacon of the Anglican Church of Hawaii and traveled with its founder Queen Emma to Europe between 1865 and 1866, circumnavigating the globe upon his return eastward via New Zealand.

His father was a successful Hawaiian politician, judge and entrepreneur who owed his rise to prominence to High Chief Hoapili, a trusted friend and companion of King Kamehameha I and the Governor of Maui, who became the child's namesake.

[6] On July 1, 1856, Kaʻauwai married Mary Ann Kiliwehi (1840–1873), daughter of High Chiefess Kuini Liliha, Governess of Oahu, but they had no children.

He became an aide-de-camp to King Kamehameha IV and converted from Congregationalism to the Anglican Church of Hawaii established by the Anglophile monarch and his wife Queen Emma.

On September 25, 1864, he was ordained as a deacon by Bishop Thomas Nettleship Staley in Lahaina, the only Native Hawaiian to have this distinction, and afterward assisted the Archdeacon Reverend George Mason on the island of Maui.

[7][8][9] After Kamehameha IV's death, Queen Emma decided to travel to England to solicit donations for erecting a cathedral in Honolulu and continued the legacy of her husband.

They returned to London where they proceeded on to Auckland, New Zealand without the knowledge or permission of Queen Emma or King Kamehameha V. Prior to leaving England, Kaʻauwai had written to the Hawaiian Minister of Finance Charles Coffin Harris indicating they intended to take a "rather long round-about, and slow way toward home".

With his mistress Keanolani (or Keauookalau, the wife of Lihilihi, of Kauai), he had an illegitimate son named William Hoapili Kaʻauwai II, born on January 31, 1874.