He said "Convivenza" which literally means "living with"..the same terminology is used in Italian-- same word --and it means exactly that.. I sure wish it didn't but it means living in common law.
On this article, it confirms it. https://www.catholicnewsagency.com/...-union-not-mistranslated-in-documentary-95995
I've done professional translation work from Spanish and I would not have translated what he said as civil union. There is a term for civil union in Spanish and it is unión civil. Francis said "lo que tenemos que hacer es una ley de convivencia civil". I would have translated that as what we need to make is a law for civil cohabitation. As far as I'm concerned it's just semantics as either of those things are against church teaching but I think he chose his words very carefully and they weren't translated well.