"They are a couple of husband and wife."
Translation:Mereka adalah pasangan suami dan istri.
We could improve the translation, i think, by saying: "They are a couple, husband and wife." or "They are a couple: a husband and wife." The confusion, i believe, is from the ambiguity of "couple" in English. So, the English gloss for the Bahasa statement should not have included "couple of" since that combination is used most commonly with the non-matrimonial meaning.
"a husband and wife couple" sounds clunky, but in 2021 and beyond, we'll hear it more often (as compared to a husband-husband couple, a wife-wife couple, etc)
Though the English accuracy isn't as important as the Indonesian structure. You cannot translate word for word and expect to sound anything like a native speaker. Just internalize the structure and move along...