You people are all nuts. There was only *one* Vivi and you hallucinated the others! You were seeing double! Or rather, the magnified version of it...
I'm not satisfied by the ending of IX, especially the peculiar Vivi clones. They could've at least had the decency to make them look slightly different...unless he was directly cloned. So I doubt that they used a machine to make more mages, why would they choose the little Vivi-model one?
And as for the Vivi-Quina marriage...I'm sure that failed after Quina realised that Vivi wasn't really interested in food.