How do we know that Nick Locarno wasn't just a name Tom Paris just used while attending Starfleet? His dad was famous and a iral. Maybe he wouldn't want just everyone knowing he was a son to a major Starfleet captain/iral. They could of just had tom Paris say he went by Nick Locarno while at the academy in lower decks. Children of famous people have done this before and gone by a different name as to not get special treatment because of their parents. That's how I felt that it was when I watched Voyager