Minnie,
Just because the census says they are married, doesn't mean they are! (or ever were!)
Also, ages on the census may not be correct either!
This may be difficult to crack as they both may have been under 21 at the time and did not have permission to marry so did not marry but carried on as if they were.
Also, if George was younger than his "wife" then they may have lied about this to "save face".
I've looked for the births and marriages but this could be a possibility for George's birth. Cannot find any trace of their marriage either.
George Blackley Mar 1864 Chorlton 8c/596
This would mean he was 16 at the birth of his daughter and possibly younger than his "wife". It may not be him, of course, just a theory.
Also, have you found this family in 1891 or 1901 - worth checking to see if their "ages" change over the years and also any further children, etc.
Good luck,
Claudia