Not sure if it's the same with HAL, but on a recent Alaska cruise with my sister on Royal we linked reservations and we could see all the details of each other's booking.
She was a little ticked when she saw that we paid nearly $1000 less for the same cabin. I said, "Sis, we booked 8-months before you did!" She still hasn't completely gotten over it. π
Sometimes it's best to keep things separate.