James St John Phillips, the son of JAMES JOHN PHILLIPS and his wife Elizabeth Kent Appleby, was born in Co. Antrim on 17 February 1870. He studied engineering at Queen's College, Belfast, from 1887 until 1890, when he gained his B.Eng. degree from the Royal University of Ireland.
From 1889 he was also articled to his father, with whom he remained as an assistant after completing his pupilage. He became his father's partner circa 1896. The partnership lasted for about ten years; the last mention of it in the Irish Builder is in the issue for 18 November 1905. After this date he appears to have practiced on his own. In 1919 he received a commendation for his design for industrial dwellings in Part I of the RIAI and Local Government Board competition for urban housing. Like his father, he received a number of commissions from the Methodist church and he also did a great deal of commercial and domestic work. He was a high ranking mason and was Grand Superintendent of Works for the Province of Antrim. From about 1927 he was architect to the Armagh County Regional Education Committee, designing several schools.
Phillips died in the summer of 1935, predeceasing his father by a few months. At the time of the 1911 census he had been married to his wife, Beatrice L. Phillips, for ten years but had no children. He later married a Miss C. Carty from Dublin. According to his obituarist in the Irish Builder he had a variety of skills; he was a good musician, had a discriminating eye for paintings, and frequently acted as a judge at dog shows. He was honorary secretary of the Belfast Naturalists' Field Club.