Thanks, Jean. William Callow & Mary Corkill certainly look like the right family for Margaret.
William Callow & Mary Corkill married Maughold 11 Sep 1837.
Margaret bapt 2 Jul 1837.
Siblings:
CALLOW Mary [daur of] William Callow/ Mary Corkill [bapt] Parish Church 6 Jun 1839
CALLOW Jane William Callow/ Mary Corkill Parish Church 9 Jan 1842
CALLOW William William Callow/ Mary Corkill Parish Church 24 Mar 1844
CALLOW Ann William Callow/ Mary Corkill Parish Church 16 Sep 1846
CALLOW Elinor William Callow/ Mary Corkill Parish Church 11 Mar 1849
CALLOW Rebecca Esther William Callow/ Mary Parish Church 3 Aug 1851

Kevin, this is Tom Corteen's transcript of the Maughold 1841 census (ages rounded, no relationships given):
2 12 61 Pt of Ballakilley
William CALLOW 20 Tailor Isle of Man
Mary CALLOW 30 Isle of Man
Margaret CALLOW 4 Isle of Man
Mary CALLOW 2 Isle of Man

There are also:
2 3 12 Ballajorey
William CALLOW 60 Woollen & linen Weaver Isle of Man
John CALLOW 55 Tailor Isle of Man
[I'll check these to see whether related.]

Maughold 1861 census:
1 40 Croit Ranch House
William CALLOW Head MAR 45 Proprietor of land farming 2 acres Maughold
Mary CALLOW Wife MAR 50 Maughold
William CALLOW Son UNM 17 Labourer Maughold
Ann CALLOW Daughter UNM 15 Maughold
Rebecca Esther CALLOW Daughter UNM 12 Maughold
Robert H STEPHEN Nephew UNM 1 Maughold

Also 1861:
3 46 Ballacorteen
Robert BREW Head MAR 22 Shoemaker Maughold
Jane BREW Wife MAR 20 Maughold
Jemima BREW Daughter UNM 1 Maughold

Married 2 Jun 1860
Robert BREW Full age Bachelor Labourer Maughold [father] John Brew, Labourer, and
Jane CLAGUE Full age Spinster Ramsey [father] Thomas Clague, Mason
.............

Sorry, Jean, I didn't see your second message while I was writing this.

Sue