I had a completely new thought on the matter.
Remember that time when Harry as being a dick in the Omega Directive proving that he wasn't a team player who couldn't follow orders (Well unless it was a Hirogen dipping a rifle barrel his throat telling his how to be a treasonous race traitor.) and Seven decided that he was too poor at his assigned task that he was redesignated with a different name to symbolize demoted repositioning in the work detail?
Anika probably had plenty of different Jobs in the Collective over the years and numerous different designations which were specific to each job. Her name kept changing and it was like winning a game of roulette that her name was "Seven of Nine" when she met the Voyager Crew.
If Seven marries Chuckles, they became a new subcollective of just two, and she might be concerned by the nature of "exactness" to change her name to a title fitting her position a part of the two.
So which one of them is one of Two and which one of them is Two of Two?
I believe the fairest way to sort it out might be that whichever one of them cowboys up and actually does the proposing is One of Two more so than... And their numbers would change again still as their subcollective grows as they have children. Though how would the children feel about their names being fluidic and changing every time Mommy gets knocked up? Talk about a new reason to resent the incumbent younger siblings.