Earl of Brentford was a title that was created twice in Peerage of England.
He had already been created Lord Ruthven of Ettrick in 1639 and Earl of Forth in 1642, both in the Peerage of Scotland.
He had no surviving male issue and the titles became extinct on his death in 1651.
Lord Brentford was a great-grandson of William Ruthven, 1st Lord Ruthven (see Earl of Gowrie for earlier history of the family).
Their daughter, Isabel (or Isobel), succeeded as 5th Lady Ruthven of Freeland in 1722 (see Lord Ruthven of Freeland for further history of this title).