When John Dunville [founder] died in 1851, Dunville & Co. had been a large, thriving business for many years and his surviving son William Dunville (1812-1874) succeeded him as Chairman. In 1864 William Dunville married Anne Georgina Knox, daughter of the Venerable Edmond Dalrymple Hesketh Knox, Archdeacon of Killaloe, and granddaughter of the Honourable Right Reverend Edmund Knox, Bishop of Limerick. They had one son. As well as being Chairman of Dunville & Co., William Dunville was an active member of the Liberal Party and a Justice of the Peace.

In about 1860 William Dunville took in as partners his nephew, Robert Grimshaw Dunville (1838-1910), and James Bruce and James Craig. These energetic and ambitious young men spurred the development of Dunville & Co., and with William Dunville succeeded in building the Royal Irish Distilleries. Robert Grimshaw Dunville's father John Dunville Junior had died when Robert was two, and his mother had died when he was sixteen. James Craig's son, born in Belfast in 1871 and also named James Craig, became the first Prime Minister of Northern Ireland. He was knighted and later created Viscount Craigavon of Stormont.

A charitable trust, the Sorella Trust, was founded by William Dunville in memory of his unmarried sister Sarah (1817-1863). Sorella is the Italian word for sister. The initial aim of the trust was to improve the houses of the working classes and this was achieved by building better houses in the Grosvenor Road area. Sorella Street was named after the trust. Further money from the trust, which had been supplemented by rent from the houses, was used to fund scholarships for primary and secondary education, and for exhibitions to Queen's College, which became Queen's University Belfast.

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William's nephew, John Dunville Junior's son, Robert Grimshaw Dunville married in 1865 Jeannie Chaine, daughter of William Chaine of Moylena. In 1866 Robert built the magnificent Redburn House, two miles along the Holywood Road from Richmond Lodge, where his uncle William was living. Redburn House was designed by the architects Lanyon, Lynn and Lanyon. It had seventy rooms, the most grand of which were the entrance hall and the ballroom, and it was set in one hundred and seventy acres of land, with views of Belfast Lough and the hills of Antrim. Robert and Jeannie's son, John Dunville Dunville (1866-1929), was the first member of the family to be born in Redburn House.