Yes, and no. A Sonos system can consist of up to 32 devices. But you can only put a stereo pair of Sonos Ones in a Sonos ‘room’, so in order to have twelve, you’d need at least 6 Sonos ‘rooms’, and if they were not stereo pairs, you would need twelve Sonos ‘rooms’. However, you can certainly group them all together, and they’d be in sync.

But a “room” is just a label to identify a speaker/speaker set, so don’t think “physical” rooms

Thank you!

So, let 2 and 2 be defined as pairs.

Room 1 will have three pairs, and room 2 will have three pairs.

Then I can group all pairs in room 1 and the same for room 2, and then combine freely if I want to play music in one single room or both rooms combined, as I understand you :-)

Well, not really. Again, the most Sonos Ones that can be in the Sonos software’s ‘room’ is a pair. 

So in your physical room, you’ll have 6 Sonos ‘rooms’, each with a pair of speakers, and you’ll then ‘group’ all 6 rooms so that they play the same thing. 

Once you actually ‘do’ this, it becomes pretty clear.