Admiral Janeway sabotaged that union by first telling them both that they are fates bitches, and second just because they had made the best choice from limited options, the admiral seriously expanded the happy couples human dating pool by trillions, which means that the choices they made were bullshit.
Everything Admiral Janeway said to her child version of herself, had to have been a lie to make sure that when Captain Janeway rebelled against her (She's a Scorpion, it's in her nature. Oh, you thought the Borg were the Scorpion? Then why was Seven so helpful in Shattered?) to force the opposite of what she said that she wanted, until what really came to pass was exactly what the senior Katherine had in mind all along.
Was Seven having sex with the Hologram Chokotay?
That's a pretty serious fricking clue she wanted his babies.