CAT 12 Question

[FreeTime]

I thought that CAT 12's only sleep 3 but you can book and will automatically be upgrade to an 11. However the DCL website actually advertises 3 or 4.

Here is my dilemma. I have a CAT 9 and CAT 12 booked. 1 adult and 2 kids in the 9 and 2 adults in the 12. My DH is booked in the 12 with FIL and plans on sleeping in the cabin with us. I want to downgrade. Can I actually get a 12 that will sleep the 4 of us, or do I need to book the 11?

Thank you!