That’s what I thought it would all come down to... Was the marriage legit in the first place?
I would suggest that most aren’t. Even if they have been successful, even those weren’t legit. They were just lucky...
I would say regarding the marriages that got started on an immature footing, and yet turned out to be long lasting and reasonably happy, that at some point, God and the couple got together.
It’s an indication of how much marriage really is a thing that we are designed to do, and find contentment in— that even immature, selfish fools can eventually get it going right, with God’s grace.