Hello Joss C.
Your family are in Kilmarnock, 1851 census, this is only a index so limited information, you can get the original at Scotlandspeople, also their name is down as Rox, but its no doubt them.
James Rox, age 26 years,
Elizabeth Rox, age 28 years,
Edward Rox, age 2 years,
William Rox, age 1 year.
I doubt however you will find a marriage, or births, for them or the children, before 1855. in Scotland it was not compulsory to register births or marriages.
Regards,
Jonn.