 His brother Henry de Beaumont was a central figure in the Scottish Wars who claimed the title of Earl of Buchan through his marriage to John Comyn's niece Alice and his sister was Isabella de Beaumont, wife of John de Vesci.In 1316 Lewis was certified as one of the Lords of the Nottinghamshire towns of North Leverton, Habilsthorp and Cotes.Lewis was serving as Treasurer of Salisbury when he was nominated to be Bishop of Durham on 9 February 1317, thanks to the efforts of his countrywoman, Queen Isabella He was confirmed at Westminster on 11 September 1317 and was consecrated in Durham on 26 March 1318.