I really can't believe that people would think they could go out and have sex with someone and think that somehow makes them married.
That is the very definition of fornication...sex before marriage.
Scripture also tells us to follow the laws of the land. In order to be legally married, you have to get a marriage license and then have it officiated.
If you don't do that and go out and have sex with someone then you are fornicating and that is plain and simple.
And really if you pray about it and feel like it is the person that God wants you to marry then why wouldn't you want to do it legally.
Have you ever met a Christian who lived with a person and said they were married in the eyes of the Lord and did not need a legal paper and then broke up, who then told people they were divorced? Ever?
What does that tell you? They were lying to themselves and they know it. They don't try and keep the lie going after the break up by saying they are divorced. Instead they claim they have never been married if asked.
Also have you noticed that those who marry out of guilt of living together in fornication and trying to convince God that they are married but feel guilty and then decide that they should get married to "make it right" that most of these marriages do not work out?
Why? Because neither is ready for marriage. Both are not strong Christians. If you are looking for a Godly person you don't want to choose the one who is willing to live with you in fornication. So that is the first big red flag that they are not the one for you. But you are not the one for them either. Both need to seek the Lord and live out a mature life of no compromise for a couple of years and then only accept those who are NOT WILLING to live together first as a potential mate.
Also those who do think that getting married will "make it right" are wrong.
Getting married will not remove the sin they were doing. Only the Blood of Jesus can do that. They must confess their sin and call it what it is.
Then they need to understand that they
do not HAVE to get married to make it right. Instead, they need to separate and not live together and not have sex. They are under no obligation to get married. If they decide that is what they want to do then fine but guilt or making things right should not be part of the decision process. They don't have to get married to make it right. Getting married would never make it right.
What they did was sin and repentance and stopping it will be what is right. They might discover that once the "we have to do this to make what we were doing not be a sin" is not possible and no longer part of the decision process, then they may discover that they don't really want to get married after all and go their separate ways. Breathing a sigh of relief that they almost did what many of these couples do and lock themselves into a lifetime of misery in an attempt to "make something not a sin" that was still a sin.