As you may be aware, a lot of the parish records for the Island are on the IGI (at www.familysearch.org). A search for William Brew and Margaret Quayle on this site gives us :-

One marriage (twice) of a William Brew and Margaret Quayle in the IGI – on 2 Feb 1813 at Braddan, Isle Of Man.

There are 23 matches for children. When you eliminate all the duplicate entries these are:

Robert BREW Christening: 6 Jul 1816 Kirk Braddon, Isle Of Man, England
William BREW Christening: 30 Aug 1818 Kirk Braddon, Isle Of Man
Martha BREW Christening: 17 Sep 1820 Kirk Braddon, Isle Of Man
Elizabeth BREW Christening: 3 Mar 1823 Kirk Braddon, Isle Of Man
William BREW Christening: 23 Oct 1825 Kirk Braddon, Isle Of Man, England (or Saint George, Douglas, Isle Of Man)
John Thomas BREW Christening: 30 Apr 1828 Kirk Braddon, Isle Of Man(or Saint Mathews, Douglas,)
Thomas Christening: 9 Oct 1831 Kirk Braddon, Isle Of Man, England (or Saint Mathews, Douglas, Isle Of Man)
James BREW M Christening: 26 Oct 1834 Kirk Braddon, Isle Of Man(or Saint Mathews, Douglas, Isle Of Man

- they all appear to be one family - and seem to fit your Martha, Elizabeth, Thomas, John and William quite well!

Roger