[Rowlf]

I have done family history too and find that ages do not always tally. People then did not always know how old they were. As for the marriage certificate sometimes it will give the exact age and sometimes when it gives '21' it means they were over that age.
On some it only says 'Full age' again meaning over 21 which ofcourse was the legal age of adulthood. On some Census you will see they do not always age 10years as you would expect. Sometimes less sometimes more than 10years. It can be very confusing but keep at it.It is a very addictive passtime.Good luck with your research.