The brothers James and Walter McDonald were born in the townland of Nicholastown, Mooncoin parish, County Kilkenny, Ireland, James on 10 August 1824, Walter on 14 December 1830. Their parents were Richard McDonald, farmer, and his wife, Ellen Keefe. The two brothers trained for the priesthood at All Hallows, Dublin: James was ordained there in 1851; Walter in Auckland, New Zealand, on 9 March 1856 by Bishop J. B. F. Pompallier.
When the McDonalds came to Auckland, Pompallier was in the process of establishing his diocese after the removal of the Marist fathers to Wellington. The two brothers became his loyal lieutenants in this work, and also his close friends. After his arrival on 9 March 1852 James was given charge of St Mary's, North Shore, where there was a school for Maori, a seminary and a farm. It was there that he started his lifelong association with the Maori. In 1853 he was appointed vicar general, and while remaining in general charge of the seminary and boys' school (both removed to Freeman's Bay in 1853), he also travelled extensively in the Auckland diocese (virtually coterminous with the Auckland province). For 16 years he represented a bishop who was more than 20 years older, heavy in body and afflicted with arthritis. Among other tasks, for some 18 months in 1859–60 he took charge of the diocese during Pompallier's absence overseas, and in 1865 he became inspector of Catholic schools. From the mid 1860s he also became more closely involved in mission work among the Maori.
Walter, who came to Auckland as a deacon in 1855, was private secretary to the bishop from 1856 to 1869. He learned to speak Maori, as had his brother, and was able to visit both Maori and European areas on the bishop's behalf. For three years he was responsible for the Bay of Islands and the east coast of Northland, travelling by sea from Auckland at regular intervals. In the early 1860s he looked after the area from North Shore to Puhoi.
With the resignation of Pompallier in 1869 and the questions that arose concerning his diocesan administration, it was almost inevitable that the two brothers who had been so closely connected with him should now be removed. In 1869 James, who had become apostolic administrator after Pompallier's departure in 1868, was appointed parish priest at Drury, and in 1871 Walter was made administrator of St Patrick's Cathedral, that is, parish priest of Auckland city. Both brothers proceeded to become legends, displaying even more flair for parish than for administrative work.
As well as giving pastoral care to the settlers of the Drury district, James travelled long distances from his hut at Ramarama to visit the Maori districts not only in his parish, which extended from Papakura to Drury and from the Tasman Sea to the Hauraki Gulf, but also throughout the entire Auckland diocese. Wherever he went, he baptised, married, celebrated Mass but above all brought the comforts of a priest's presence to Maori Catholics almost totally neglected by other priests in the aftermath of the wars of the 1860s. The Maori found in Maketenara (as James was called by them) a man who loved them, and they returned his love along with a growing reverence which gradually elevated him in their eyes to the status of a prophet. James's growing stature was recognised by Auckland's bishops: Bishop T. W. Croke remarked, 'His people love him'; in 1880 Archbishop Walter Steins relieved him of responsibility for Drury and put him in charge of all the Maori in the diocese; by 1883 Bishop J. E. Luck had appointed him vicar general for the Maori in the diocese.
But the arrival of Bishop Luck also brought changes of direction for both brothers. At base there is thought to have been a lack of empathy between the English bishop and the Irish priests. When Luck began to negotiate with the Mill Hill fathers to take over the Maori missions, James opposed the move. In 1887 he was given the missions north of Auckland and the Mill Hill fathers those south of Auckland. He went to live at Hokianga. In 1886 Bishop Luck appointed Walter papal chamberlain (monsignor) and shifted him to the parish of Panmure, amid furious protests from the general public: in his position at the cathedral Father Walter had become immensely popular with the people of Auckland – Catholics and non-Catholics, adults and children, respectable and not so respectable. But he had become rather too much of a public figure for the liking of Bishop Luck. Luck may also have suspected him of collusion with James in resisting the advent of the Mill Hill fathers. At Panmure, however, Walter's popularity continued to grow; he became chaplain to Ellerslie racecourse and even clerk of the course for a time.
After some 40-odd years of service in the diocese both brothers died in the 1890s – James at Purakau in Hokianga on 6 July 1890, Walter on 31 December 1899 in Auckland. James, who had been the bridge between the pre-war Catholic Maori missions and the Mill Hill fathers who resumed this work in the 1880s, was buried beside his brother's parish church in Panmure. Walter was also buried there, after a funeral procession which had started from St Patrick's in the city and which was reported to be one of the largest Auckland had ever seen.