I have shared a cabin with my mum and my sister on Oceana. The only problem was that no-one really wanted to sleep on the top bunk and because both my sister and I were pregnant at the time this made things difficult.
Best wishes, Samantha.
We took my 18 year old daughter on oceana and it was a little cramped although you dont spend a lot of time in cabin. We have booked for 2010 and taking my mum but have choosen an outside cabin as thase are bigger.