Well, I personally would never call anyone "mixed race", but presumably the term covers an Asian and a European who have had offspring, or the children of an African and either of the above.
I don't see why we should concern ourselves about a person's antecedents. Medically there is so little difference between the so-called races that I doubt it serves any useful purpose to talk of mixed race.
In many cultural contexts it may be relevant that NN's mother is Asian, or MM's father European, but then we can surely say so.
Do you still wear you original wedding and engagement ring