Here is some interesting stuff about common law marriage and Christianity:
Is Common Law Marriage Biblical?
The biblical ideal of marriage involves covenantal commitment, public recognition, and a lifelong bond.
Following this logic, polygynous Mormon marriages would qualify (they have special ceremonies for their "spiritual marriages", they are recognised by wider community, and they tend to stay together); while simple cohabitation wouldn't. Common law marriages are more of a grey area. I wonder if they would fall under the category of "concubinage''?
I was also surprised that the parents' consent was not even mentioned, but it was paramount in the Bible, both OT and NT.
What do you think?