[lsb]

Also, if you want to do it right, use a dual form for expressing a pair, -o. One Winkelvos, two Winkelvo, a family of Winkelvi.

Duals are used for pairs or things, like eyes or hands, in Latin and Ancient Greek. In Sanskrit, duals are even more common. (Respect your elders, learn some outmoded grammar today!)

[gte910h]

I don't remember anything about pairs being a special case in Latin (At least roman style Latin, not catholic style Latin), even in the 3rd declension nouns (which are the ones that pluralize via -i).

[lsb]

As far as I recall, it's mostly duo, ambo, and 2nd declension nouns by analogy in archaizing poetic passages.