Kelly, William (1821–1906), biblical critic and Brethren leader, was born in May 1821 in the townland of Ballyfrennis, near Millisle, Co. Down, the only son of William Kelly, a presbyterian, described as a ‘gentleman’, who died 14 April 1823, aged twenty-five, when William was not yet two years old; there was also one daughter. William had several tutors, and attended the school at Rademon, Co. Down founded by Moses Neilson, father of the presbyterian clergyman William Neilson (qv). He entered TCD in 1836 and graduated in 1841 with the highest honours in classics, and then became a tutor in the family of the seigneur of Sark. He had been attending the established church and was for a time drawn to the Oxford Movement, attracted by the ideas of Pusey and the sermons of John Henry Newman (qv). Following a conversion experience in 1841, he left the anglican communion and joined the Plymouth Brethren, later becoming a close associate of John Nelson Darby (qv), whom he met in 1845 in Guernsey. He was influential among the Brethren for the rest of his life as a noted lecturer and preacher. He seems to have had independent means and was able to devote much of his time and energy to the interpretation of the Bible, and also to the explication of Darby's theological views. He revised Darby's Synopsis of the Bible (1857), and also edited his collected writings (thirty-four volumes and a supplement, 1867–83).
Kelly himself wrote and published prolifically, preparing commentaries and textual notes on every book of the Bible; he was one of the most notable biblical scholars in Britain during the nineteenth century. From 1848 to 1850 he edited and wrote for a journal called the Prospect, the forerunner of the Bible Treasury, which he edited from 1856 to February 1906, the month before his death. From 1854 to 1856 he wrote for the Christian Annotator, to which evangelicals, especially those attached to the Exclusive Brethren, contributed. His reputation as a keen critic and controversialist, along with his opposition to many aspects of what was known as the ‘higher biblical criticism’, secured for him a degree of celebrity and a considerable readership, even among those who held other views on doctrinal matters. Some of his works continue to be read, though mainly among the Brethren. Like Darby, Kelly called for a strict adherence to all tenets of doctrine and practice of the Exclusive Brethren, and was a firm believer in premillennialism.
In 1879, when the Exclusive Brethren disagreed over the excommunication of Edward Cronin (qv), Kelly broke away from Darby to lead the more accommodating faction in the dispute. Two years later he founded a separate and independent assembly, the ‘Kellyites’, which he led until his death. After almost thirty years in Guernsey, in 1871 Kelly moved to London, and spent the rest of his life at Blackheath. He died 27 March 1906 at a friend's house, The Firs, Denmark Road, Exeter. He married firstly Elizabeth Montgomery, who was from Ulster but at the time of their marriage living in Guernsey. After her death in 1850, he married, in 1857, Elizabeth Emily Gipps (1831–84), daughter of Henry Gipps (d. 1832), the evangelical rector of St Peter's, Hereford; she was an accomplished linguist, who assisted her husband, notably in his translation of the Psalms (1905), half of which was her work. Four daughters and a son were born to the couple between 1858 and 1873. Shortly before he died Kelly presented his huge library of 15,000 volumes, weighing 17 tons, to the town of Middlesbrough.