How can I mirror two macbooks
You could setup a Mac OS X Server and boot from the network, however you will need to have a third Mac, which might be costly unless you have an old one.
You can purchase the Server from the AppStore for $20. However, booting your Mac from your server requires a moderate internet connection as well as a quick bandwidth (at the place where the server is and your location) in order to work well.
The server offers a service called NetInstall that will allow you to boot from the server. More information how to active it can be obtained in the server documents in Update client software -> Provide NetInstall service).