It depends, when and where did the marriage take place? Does the certificate list their ages?
Have you found them in any census? Do you have their birth details etc
Curious as to how you got the certificate without looking up some of the above? Did someone pass it on to you?
Oh and well done on `completing` your family tree! :)
I`ve been researching mine for almost 10 years and I`m nowhere near!

If you`d like to post some names and dates, I`m sure many will be willing to help.

Jacki