My friend (U.S. citizen) and his Columbian fiancée recently got married civilly for citizenship purposes. They were living at his parent’s house in separate rooms and planned to do so until their Catholic wedding in January 2014. He bought a house but they didn’t plan to move in together until after the Catholic wedding. However, the Catholic priest that is preparing them told them it’s ok to live together in their new house now (September 2013). He gave them his blessing and said it would be good for them to away from his parents!
I’m confused. If they have sex now, is it considered a mortal sin by the Catholic church?
Should I recognize their marriage since the priest apparently did?
Is their civil marriage ok in God’s eyes?