Hi Viv
I don't know if you've already found them in 1841 and 1851, but if you haven't, this might be their family in 1841---it's the only Kewley family at that time in IOM census which has both an Edward and a Thomas of roughly the right ages. Ancestry has mistranscribed their name as Kudej but it is clearly Kewley on the original.
Catherine Kudej 1 6 Mo
Edward Kudej 6
John Kudej 10
Margaret Kudej 40
Margaret Kudej 14
Matthias Kudej 55
Thomas Kudej 5
William Kudej 8
Matthias is an ag lab. I can't decipher the name of the place where they live---it's in Santon district 3 page 1.
In 1851, I think that this is the same family---Edward isn't there though, and Margaret is now a widow washerwoman. They're living at Braddan.
Catharine Kewley 11
James Kewley 8
John Kewley 20
Margaret Kewley 51
Thomas Kewley 13
Jean