How do I merge two Mac Minis into one with separate user accounts?

My wife and i each have our own mac minis. They are very old so we are considering buying 1 new mac mini and setting up 2 users on it and sharing it.

Is it possible to transfer our data from the old macs (via time machine back ups) to the new shared mac? If so, i am looking for some details so i do not screw it up.

[Re-Titled by Moderator]