Would you expect to see parent's names on an 1848 NSW marriage certificate?
Hit and miss, so to write.
If either party is under 21 years, then you expect to see name and relationship of person giving consent.
Images of NSW C of E marriages from that era are found via RChat's NSW Resources Board and live links to Christ Church Cathedral, Newcastle parish registers (earliest from about 1820, and continuing into 20th Century too).
Here:
Baptisms, Marriages, Burials, Christ Church Cathedral, Newcastle
http://www.flickr.com/photos/uon/sets/72157606066769147/ 1820 – 1899 Family Register
http://www.flickr.com/photos/uon/sets/72157605008173551/ 1826 – 1837 Baptisms, Marriages, Burials
http://www.flickr.com/photos/uon/sets/72157604433014652/ 1837 – 1838 Baptisms, Marriages, Burials
http://www.flickr.com/photos/uon/sets/72157605132739200/ 1839 – 1861 Baptisms, Marriages, Burials
http://www.flickr.com/photos/uon/sets/72157605674610949/ 1856 – 1868 Marriages Register
http://www.flickr.com/photos/uon/sets/72157605785759029/ 1869 – 1885 Marriages Register
http://www.flickr.com/photos/uon/sets/72157605802132868/ 1885 – 1897 Marriages Register
http://www.flickr.com/photos/uon/sets/72157606197590347/ 1899 – 1913 Marriages Register
http://www.flickr.com/photos/uon/sets/72157605928662968/ 1913 – 1914 Marriages Register
http://www.flickr.com/photos/uon/sets/72157606308436455/ 1914 – 1916 Marriages Register
http://www.flickr.com/photos/uon/sets/72157606323070651/ 1916 – 1918 Marriages Register
http://www.flickr.com/photos/uon/sets/72157606450662513/ 1918 – 1929 Marriage Register
http://www.flickr.com/photos/uon/sets/72157606952230042/ 1929 – 1936 Marriages Register
ADD, On several of my ancestors 1840s NSW marriage certs, you can see where the Rev'd has recorded their age (often in white space to the left where they would sign). On the Newcastle images you can see where the Rev'd there has sometimes recorded the age, and sometimes the ship of arrival too. Usually this is where either bride or groom is still serving a sentence, and so the register would also record "with permission of the Governor". Sometimes the age is recorded even when both are over 21, and both were born in the colony. There was no auditor/regulator checking that the clergy of each denomination all recorded same depth of information as each other, (or even if same clergyman was consistent in what he recorded)..... hence my Hit and miss expression....
. The C of E Family sheet register is an alternative, however, these are not as well conserved, and many simply have been lost over the decades..... And, not all denominations had a similar "cheat sheet" option for their clergy even for those on rural circuits.
Cheers, JM