Does an attached bathroom make a master suite?

Yes you can list a house with two master suites. Typically, this is found in a rambler with the master suites on separate wings of the home.

Generally yes. A primary or master suite is usually defined as a bedroom with a private attached bathroom, and often a walk-in closet. The key feature is that the bathroom is private to that bedroom.

You say "attached," are the bathrooms directly accessible to the bedroom or do you have to go into a hall way first to access another door? If you have a bedroom that has direct access to its own bathroom then you should be able to list it as a master suite.