No - each time it is encrypted it will be different as it has a random seed at the start, even if you are using the same password.
It has to be like this otherwise the cipher would be vulnerable to an attack.
You would work around though. Assuming you are backing up to a directory called A for the first computer and B for the second. What you could do is copy A to B before you sync the second computer. It will then delete all the files that aren't a match but keeping all the ones which are.
If you wanted to do this on a regular basis you could investigate the --copy-dest flag or the --compare-dest flag which you'd use to server side copy or ignore files in A when you were doing the sync for B.