According to the certificate that
Gadget looked at, Margaret Fraser had married a Mr Imlah, and the IGI lists the marriage as Margaret Dunbar Fraser to James Imlah in 1863 in Aberdeen. A Margaret Imlah or Fraser died in Scotland in 1904, aged 66. You would have to check that this one's death certificate matches the one in the marriage certificate of course, but it looks very likely that this is the mother of Charles Fraser. If she is, and assuming that her age on the death certificate is accurate, she was born in 1837/8, and she did not emigrate to Canada.
According to the IGI, Margaret Dunbar Fraser and James Imlach had four children
Joan Bonna Fraser, born 5 September 1864 in Keith
Margaret Thomson Fraser, born 20 March 1867 in Keith
Jane Fraser Imlah, born 11 November 1868, birth registered both in Strichen and in Abernethy and Kincardine
James, born 30 May 1871 in Abernethy and Kincardine
William Forsyth, born 29 June 1874 in Abernethy and Kincardine
but there could be more because the IGI stops at 1874/5.
Unfortunately I don't have access to my 1881 census CD-ROM just now, but when I do I'll look them up and check Margaret's birthplace.
daisypetals, you wrote,
I didn't mean to imply that Margaret had Thirlow illegitimately.
The absence of a father's name on a birth certificate always indicates that the child was illegitimate. The law assumes that the father of the child of a married woman is the husband, unless the woman specifically declares that he is not. So you didn't have to imply it or otherwise, it was perfectly obvious from the entry in the IGI.
What is confusing is the spelling of the name Thurlow (Thirlow or Thurlew, or...).
Just be thankful you are not trying to cope with the 53 documented ways of spelling the surname 'Taylor' then. Or the almost uncountable ways of spelling MacDonald or MacGregor. In 'Scotland's People' use 'th*rl*' and it will pick up all the spelling variants.