Bonsoir Jean, Actually, «un couple et son enfant» --> is best translated as «a couple and his infant», for example, a friend of the couple and the friend's infant is with the couple. «Un couple et leur enfant» --> is best translated as «a couple and their child». J'espère que ma réponse vous aiderait. Bonne chance et bonne continuation dans vos études en français, la langue de Molière et qui a été utilisé par le monde français depuis l’époque d’Hugues Capet Ron (also a non-native speaker)

One other thought for an example: «un couple et son enfant» the inference could also be a couple and the son of one of the persons comprising the couple.

Thanks Ron, However I guess I didn't make my question clear. It's not the translation I needed. I have seen both sentences written in cases where it is a married couple with their own child, child of both parents, and I wanted to know which form was correct. Maybe they are both correct, maybe one is pre-1990 and one is post-1990 French perhaps ? Maybe one is Belgian or Canadian French ? But in any case, the real question is whether the word couple is treated as a unit or as two in this case. It seems clear when one doesn't have to use a possessive pronoun. One say " Un couple chante " and not " un couple chantent" for example, but it gets a bit fuzzy when the son or leur is in play.

The spontaneous answer of a French native speaker was "leur". Apparently one tends to focus more on the two people forming the couple than the couple as an independent entity. -- Chris.

Thanks Chris. "Leur" sounds more natural to me too as an anglophone, although I know that is not the best way to determine correct usage in French!

Thanks Cécile.