A bathroom receptacle must be served with a 20 amp circuit (#12 on a 20 amp breaker).
Here's where the confusion starts, because you have some options:
1) That 20 amp circuit may serve everything in just one bathroom,
-or-
2) That 20 amp circuit may serve only receptacles in multiple bathrooms.
IF a circuit serves a bathroom receptacle and anything else (like lights and fans) it may not leave the bathroom to serve other stuff. If the circuit serves only a bathroom receptacle, it may leave that bathroom only to serve another bathroom receptacle.
If you can arrange it so that you can serve your bath receptacles off one 20 amp circuit, and then do the fans and light off another 15 or 20 amp circuit, you will be in compliance. The circuit that serves the fans and lights in the bathroom(s) may serve lights and receptacles in other parts of the home if need be, and you'll still be in compliance. It's the receptacle circuit that they're fussy about.
The bathroom receptacles must be GFCI protected. Whether you do that with a GFCI breaker or a GFCI receptacle is totally up to you. The lights and fans do not need GFCI protection unless they are over the tub or shower.