Carrickbeg

They will reprice with a penalty. It makes no sense, but they force a no show. Just check the sister in as if she was going.

If you remove your Aunt from your mother's reservation, NCL will charge a penalty on the reservaton, plus your mother's fare will be repriced on single supplement. Just have your Aunt be a no show. She should receive port fees and taxes back. If she ordered any items like shore excursions or spa, etc. cancel those.

I would double check your pricing on the NCL site. They have changed how the price is calculated. It isn't until you put your full information in do you see your actual price (that includes port fees, taxes, etc.) Your TA can give you the free at sea and the price should be identical if not better (depending if they have group space allotted.) See the little tiny note they have now under the subtotal "Excl. taxes, fees and port expenses, they will be added at checkout."