William and John Deans, first and third of four sons of John Deans, a notary, and his wife, Catherine Young, were born in the parish of Kirkstyle, Riccarton, Scotland. William was baptised on 31 January 1817; John was born on 4 May 1820. Both attended schools at Kilmarnock and Colmonell and then undertook legal training. However, they expressed interest in emigrating and in preparation for this were placed on good farms in Scotland. The colonising proposals of the New Zealand Company appealed to them. William bought land orders in the Wellington scheme in 1839 and sailed from London in one of the earliest company ships, the Aurora, in September that year, arriving at Port Nicholson (Wellington) on 22 January 1840.
He was greatly disappointed to find that not all his land was available to him. Initially the land the New Zealand Company claimed to have bought was under investigation by the new government, and subsequently surveys were delayed. After arrival he farmed near Pito-one (Petone) beach and at the same time obtained a contract as a surveyor's labourer. Later he went with others on an expedition to explore the country around Whanganui and Taranaki. The distance traversed was about 650 miles. He also explored Wairarapa with a Māori whose identity is unknown, and briefly considered squatting there. By March 1841 he had shifted from Petone to Ōkiwi, on the eastern shore of the harbour.
Dissatisfied with his immediate prospects, in mid 1842 William sailed the length of the east coast of the South Island in the cutter Brothers which, under the command of Captain James Bruce, served the southern whaling stations. It is likely that during this journey Captain Bruce brought Deans to Port Levy, where he heard of the plains beyond the Port Cooper Hills (Port Hills). Phillip Ryan, a one-time whaler living at Port Levy, later recalled that Deans, Bruce and he went by whaleboat some distance up the Ōtākaro River (Avon River) and then overland through swamp. Climbing on to Ryan's shoulders, Deans sighted the bush called Putaringamotu (Potoringamotu) and exclaimed, 'That will do for me! I will make it my home.'
William returned to Wellington and informed his brother John of his proposal. John had bought land orders in the Nelson settlement six months before his arrival there on the Thomas Harrison on 25 October 1842. He was dissatisfied with his allotted land and agreed to join William. On 9 February 1843 the brothers applied to the government authorities for permission to squat near the Putaringamotu bush. No objection was raised, but consent was qualified by the instruction that settlement should not be made in the vicinity of any Māori cultivations. On 10 February 1843 William sailed for Port Levy in the 30 ton schooner Richmond, under charter from Captain Francis Sinclair and Ebenezer Hay. Also on board were John and Maria Gebbie and their children, who had emigrated from Scotland with William Deans, and Samuel and Jean Manson and their children, who had come out with John Deans. Supplies, including timber for the first house, made up the cargo. While William Deans and Samuel Manson set about building the first house at Putaringamotu, John Gebbie remained with the women and children at Port Levy. John Deans, meanwhile, had sailed from Wellington to Sydney and Newcastle, where he bought sheep and cattle. They were landed in mid June, probably at Raupaki. A rough voyage had caused rather heavy losses.
A substantial farm and a sheep run were soon established and the Deans brothers investigated the possibility of leasing the land from the Māori owners. No progress was made in the negotiations until the approval of the chief 'To-One' (Te One) was obtained. At last, on 3 December 1846, William and John Deans signed a 21 year lease for the land running six miles in every direction from Putaringamotu. Their property included the rivers Waimairi (or Waimaira), Wairarapa and Ōtākaro. The rent was £8 yearly.
Once the lease had been signed, further improvements were made to the land holding. John made voyages to Australia to buy stock in 1847 and 1850. The animals were landed at Pūrau Bay and at temporary stockyards at Camp Bay. At various times, the Deans brothers sold their livestock, potatoes and wheat at Akaroa and Wellington, their oats and barley in New Zealand and Australia and their wool in London. Gebbie and Manson sold dairy produce locally and in Wellington.
In mid 1848 the isolation of the brothers ended. The New Zealand Company and the Crown bought an extensive part of the lands of Ngāi Tahu. Soon after, the New Zealand Company delegated to the revived Canterbury Association the right to colonise an area which included the Port Cooper Plains (Canterbury Plains). The future of both farm and sheep station were now in question. The company allowed the freehold of a farm of 400 acres by exchanging the Deans's original company land orders, but would not permit any further purchases. The agreement, which was signed on Christmas Day 1848, included an important reservation provision relating to the bush at Putaringamotu; the bush stands today. Captain Joseph Thomas, acting for the New Zealand Company, agreed that the farm property should be named Riccarton and the nearby Ōtākaro River Avon, both in memory of Scotland.
Once the Canterbury Association's surveys began, it was clear that the extensive run could not remain in the control of the Deans brothers. They therefore shifted their sheep to a location of some 15,000 acres in the foothills in April 1850. This run they named Morven Hills. But when J. R. Godley, agent for the association, declared he could not grant them a licence, the brothers disposed of Morven Hills with the sheep, and claimed a run in compensation. After a lengthy dispute, in which William was the chief negotiator with Godley, the brothers were allowed to take up an extensive run named Homebush, at first provisionally, but later on lease.
As soon as the provisional arrangement was agreed to in May 1851, William sailed from Lyttelton to Australia via Wellington for more livestock. He drowned when his ship, the Maria, was wrecked near Cape Terawhiti on 23 July 1851. Shortly after his brother's death, in early 1852, John returned to Scotland. On 15 September 1852, at Riccarton, Scotland, he married Jane McIlraith, with whom he had had an understanding when he left Scotland some 10 years earlier. They sailed for New Zealand shortly after their marriage, arriving early in 1853. A son, also called John, was born later in the year. Not long after his return, John Deans senior was found to be consumptive. For some time he continued to manage affairs, but his health declined until he died at Riccarton on 23 June 1854. His death, coming so soon after that of his brother, was seen as a loss to the new settlement. In recording his death, the Lyttelton Times declared that the names of the Deans brothers should always occupy a place in the history of Canterbury.