[Verginius Rufus]

Most people don’t understand Greek and Latin plurals. Today I heard a man refer to his wife as “an alumni” of a particular university.

[Defiant]

That's fairly common usage, so common that it is almost not considered a mistake. There is a fine line between correct latin plurals, and a usage so common it becomes the English way to say it. Alumni is not quite there, but it is close.

[Red Badger]

You should have said, “Oh? You’re married to two women?”...........................B^)