Did you keep all the cruise confirmations (as pdf) emailed to you by NCL each time you book the cruises, make payments, buy shore excursions, etc. And what about the eDocs?
If you did, look at each of them (different cruises) and see the latitude number beside each passenger’s name. They should be the same number for each cruise but if they aren’t, then you have multiple latitude accounts!
Collect all the info and ask NCL to merge them into a single account number per person, and then make sure to give NCL the correct numbers when booking cruises in future.