He and his brother Joseph were the sons of a WM ironmonger in Sunderland. Their mother had been converted by John Wesley on one of his last visits. They had a strong Wesleyan upbringing and were both apprenticed as chemists. In the 1840s they went to work with the Methodist chemist John Mawson in Newcastle. In 1855 John set up his own business, dealing mainly in chemicals and metals and was also involved in lead-mining and smelting in the Pennines. He often sat under J.H. Jowett at the St. James's Congregational Church, Newcastle. His first wife Harriett and his second wife Mary were daughters of Thomas Rowland (1792-1858; e.m. 1813), who was expelled from WM in 1857 and joined the Wesleyan Reformers and the UMFC.
His brother, Sir Joseph Wilson Swan (1828-1914), born on 31 October 1828, became a partner in Mawson's business. He maintained his boyhood interest in science and invention. In 1879 he succeeded in producing an incandescent electric light bulb, at about the same time as Thomas Edison, and formed the Swan Electric Light Company in 1881. They later joined forces to establish a single electric lighting company. Mosley Street, Newcastle was lit by Swan's electric lighting in 1880. He was also one of the pioneers of photography. His achievements received only belated recognition, but he received an honorary DSc from Durham and a number of other awards, became an FRS and was knighted in 1904. His association with Methodism in his later years is said to have been 'nominal'. He died at Warlingham, Surrey on 27 May 1914.
'All his life he had cultivated the twin faculties of wonder and reverence, so that in his old age he could look out of the windows of his soul on a world which for him was full of haunting loveliness, on a universe of inviting glory, and on a mystery beyond the power of man to solve, letting the poets take his hand and lead him on where science came to a halt. 'He longed with passion seldom uttered to believe in personality's survival of death, but, hugging this hope to his heart, confessed that the evidence for so sublime a consolation was insufficient for his own conviction. Yet, though he shrank from the thought of anihilation, he was far more troubled, even in his old age, by the military activities of Christian nations. This was the one cloud on the wise serene horizon of his declining years.' Harold Begbie, in the Times, 31 October 1928, quoted in Swan (1929) p.172