Children:
David William Sturrock, b. Dundee 1831, Alexander Sturrock, Margaret Cairnie
NB: also baptism record in St Giles Without, Cripplegate, in London for someone of this name in July 1831, father Alexander, baker, mother Margaret
Maryann Sturrock, b. Dundee 1832, Alexander Sturrock, Margaret Cairney - perhaps Margaret died in childbirth?
From Freecen: 1841 Census, Seafield Lane, Dundee
Jean Sturrock, aged 66
Mary Sturrock, aged 27
David Sturrock, aged 10
Maryann Sturrock, aged 8m (?should be 8 years)
James McKechnie, aged 20m
From Ancestry, transcription, 1851 Census, Liff and Benvie, Dundee
Jane Sturrock, b. 1775, Liff, Dundee
Mary McKechnie, b. 1814, Dundee
Mary A Sturrock, b. 1833, Dundee
James McKechnie, b. 1840, Dundee
John Matthew, b. 1822, Dundee
I think you need to try to find a death certificate for Jane/Joan Sturrock (if she died after 1855) and her daughter, Mary Sturrock McKechnie from Scotland's People to find out who their parents were ... you can download these from
http://www.scotlandspeople.gov.uk/ There is a Jean Sturrock born Dundee 1775 to parents Alexander Sturrock and Jean Smart with sibling, Alexander b. 1782 (father of 'your' Alexander b. 1806??) which might be worth investigating.