Hori Kerei Taiaroa was born at Otakou, on the Otago peninsula, probably in the 1830s or early 1840s. His father was the prominent Ngai Tahu chief Te Matenga Taiaroa, of Ngai Te Ruahikihiki, and his mother was Mawera of Ngati Rangi-whakaputa. The only surviving son, he was named Huriwhenua in commemoration of a traditional peacemaking between Ngai Tahu and Te Ati Awa in 1844, when Te Maraini Huriwhenua of Te Ati Awa visited Otakou. He was christened Hori Kerei about 1858 or 1859 after former governor Sir George Grey. Older Ngai Tahu continued to call him Huriwhenua.Taiaroa grew up at Otakou, where he was taught to read and write by a European mission teacher of the Wesleyan church, of which his father had become a supporter. In the late 1850s or sometime in the 1860s, at Otakou, he married Tini Pana (Jane Burns), whose mother was of Ngai Tuahuriri of Ngai Tahu, and whose Scottish father was a farmer at Moeraki.In February 1862 Te Matenga Taiaroa dictated a testament 'To all my tribe, to my hapu, and to my son', exhorting them to see that the promises made by William Wakefield, H. T. Kemp and W. B. D. Mantell when purchasing Ngai Tahu lands were carried out. He urged them also to acknowledge the Queen's sovereignty and to treat Europeans well. Hori Kerei Taiaroa made the fulfilment of this testament his life's work.In May 1868, when the Native Land Court first sat at Dunedin, Taiaroa and Timoti Karetai applied for an investigation of the former Maori reserve in Princes Street, Dunedin, which the government had granted to the province of Otago together with over £6,000 in rents which were supposed to have been held in trust by the government for Ngai Tahu. The court declared it a matter for the Supreme Court. Subsequently, the Court of Appeal in November 1869 ruled in favour of the Otago province, and Taiaroa and Topi Patuki initiated an appeal to the Privy Council.In February 1871 Taiaroa was elected to the House of Representatives as member for Southern Maori. This he saw as a means to fulfil his father's behest. Ngai Tahu claims had been first brought to public and official notice in 1849 by the Ngai Tuahuriri chief Matiaha Tiramorehu. Tiramorehu had called for adequate pastoral lands to be reserved for Ngai Tahu under the terms of Kemp's purchase of 1848, and had sought a revision of Grey's Wairau purchase of 1847 which had recognised Ngati Toa's claim to Kaiapoi and Ngai Tahu territory to the north. Taiaroa adopted a more southern emphasis for the Ngai Tahu claims, in keeping with his father's conciliatory attitude towards Ngati Toa.In Parliament Taiaroa spoke on a wide range of issues, particularly those affecting Maori, but he made the Ngai Tahu claims his main business. In November 1871 he successfully moved that copies of the South Island land purchase deeds be printed. In August 1872 he secured the passage of a motion that the promises in Kemp's deed should be carried out, and he initiated the setting up in July that year of a committee of the House to examine 'unfulfilled promises to Natives in the Middle Island.' The committee, which included the native minister, Donald McLean, found that the claims of Ngai Tahu had not received the attention they deserved, and recommended the appointment of an impartial commission 'as a Court of equity and good conscience'. Although the recommendation was not acted on, Taiaroa had achieved the important step of getting the Ngai Tahu claims into the formal business of Parliament.In November 1872 the Otago provincial government offered Ngai Tahu £5,000 to withdraw their Privy Council case and surrender all claim to the Princes Street reserve. Taiaroa agreed to this compromise. In January 1874 Taiaroa and Patuki each received £1,000 of this money, and the rest was distributed in Otago, Canterbury and Murihiku (South OtagoSouthland). Taiaroa then applied to McLean for the £6,000 in rents, with interest; not until 1880 would this compensation be paid.Taiaroa now sought tribal support and financial backing for his work on the Ngai Tahu claims, and absolute control of the fund which was to be canvassed from the tribe. A meeting of Ngai Tahu and Ngati Mamoe chiefs was convened at Otakou marae on 4 June 1875 and a parchment was produced for their signature. By this 'Covenant' Taiaroa was to be given sole charge of the campaign, with authority to appoint lawyers, sole control of funds and complete discretion over expenditure.