Some friends of mine used to be in a couples cabin, then they had a child (and a cute one that we have babysat a few times for). After the child was born they stayed for a while longer in the couple's cabin till the time came they could move into another bigger family cabin.
Well, that day has come!
The best way to move from one cabin to another is illustrated below. You borrow the rolling rack/basket from laundry, ask permission to use the cargo elevator (if the cabin is on a different deck/floor), and then get a babysitter or take your child for a ride!
* Just in case you didn't quite figure out the other 'methods' of moving up, here it is: If single you will need to get married (to someone who also fills a position on board preferably) to 'move up' to the next size cabin. if married a baby will allow you to be put on the waiting list to 'move up' to a family cabin.
Disclaimer: Of course, I don't suggest using these last two methods just to get a bigger cabin. And I don't work for HR, so don't quote me on these methods.
But aren't the pictures cute?