Adding 3rd person to current booking

[lharry]

Final payment has not been paid yet. My son and his wife are currently booked in an interior room for 2. They are now thinking about bringing their daughter. Can they add her to their current booking and just change their room to one for 3?  Is the only difference the additional cost of the 3rd person?  Is there a $50 fee to change the booking?

[bakersdozen12]

They will need to call Carnival. It will depend on if their room can hold three (and even if it can, if the ship is currently at full capacity, they will not be able to). And if their room only holds two, then it will depend if there are any rooms for three available.