discordant couple
n.— «Jim, 31, says he and his wife, June, are “a discordant couple,” meaning that one is infected with the AIDS virus and the other isn’t.» —“Aids Threat To Women Increasing” by Kay Longcope Boston Globe (Mass.) Aug. 23, 1990. (source: Double-Tongued Dictionary)
Further reading
What if, instead of being an inanimate object, a dictionary were alive? That’s the idea behind a lavishly illustrated new children’s book called The Dictionary Story (Bookshop|Amazon) by Oliver Jeffers and Sam Winston. This is part of a...