I see from the NSW deaths index that Joseph Bogle Wardrop died in Sydney in 1899, and that his parents were William and Mary Ann. Does the actual death certificate say what her maiden surname was?
I also see from Trove and the NSW marriages index that Joseph was married in Sydney in 1863, and that he was a blacksmith.
At 233 High Street, Glasgow in 1851 were
James Hendry, head, married 43, blacksmith, born Cummertrees
Mary Hendry, wife, married, 37, born Pollokshaws
Joseph Wardrop, servant, 14, blacksmith apprentice, born Glasgow
Mary Wardrop, lodger, unmarried, 26, seamstress, born Glasgow
William Wardrop, lodger, 5, born Glasgow
Charles Wardrop, lodger, 18 months, born Glasgow
Now, it looks to me as if Mary, William and Charles may have been recorded twice in the 1851 census. But if so why?
In 1841, at 230 Castle Street, Glasgow, were
Mary Wardrop, 46
Mary Wardrop, 17
Alexr Wardrop, 15
Andrew Wardrop, 13
Isabella Wardrop, 9
Catherine Wardrop, 7
Joseph Wardrop, 5
James Hendry, 30, blacksmith
Mary Hendry, 25
all except James born in Lanarkshire.
From the index to pre-1855 births and baptisms on Scotland's People, the family of William Wardrop and Mary Hamilton included Mary, 1818; William, 1819; Mary, 1824; Alexr, 1825; Andrew, 1828; Isabella, 1832; Catherine, 1834; Joseph Bogle, 1836; George, 1839.
You could view any these baptisms at
www.scotlandspeople.gov.uk at a fraction of the cost of getting one NSW certificate (currently A$33, equivalent to GBP18.82, which would buy you 12 Scottish certificates)