His paternal grandfather, William Sewel, a Brownist of Kidderminster, emigrated from England to escape religious persecution, and married a native of Utrecht.
Returning to Holland after a sojourn of ten months, he obtained work as a translator, contributed regularly to the Amsterdam Courant and other papers, wrote verses, and conducted a periodical.
In spite of an invitation from William Penn to become master of the Quaker school opened at Bristol, Sewel remained in Amsterdam until his death on 13 March 1720.
Sewel spent 25 years on his major work, The History of the Rise, Increase, and Progress of the Christian People called Quakers.
Sewel's own work was based on a mass of correspondence, George Fox's Journal, and, for the public history, Lord Clarendon's Rebellion and Edmund Ludlow's Memoirs.