but they shouldn the doing that without telling them the gospel. Otherwise they should not even marry them and say its doomed to fail. I dont know about 200 years ago but apparently this happened with one of my former bosses, who married at 19 or some ridiculous age.
now he is separated and going with someone else but I think about his ex-wife being unfairly maligned cos they couldnt keep their vows. They arent even divorced. Its the children who then have to go back and forth etc and manage their parents separation.
If 50% of marriages end in divorce (not sure if that is it, but let's say) then 50% don't. And there are plenty of unbelievers who stay together. There are predominantly Muslim and pagan countries where the divorce rates are lower. Being an unbeliever doesn't doom one's marriage to failure, and marriage existed before Christ was born as a Man on this earth.
The Bible doesn't tell elders, pastors, overseers, priests, deacons, etc. to perform marriage ceremonies. There is nothing resembling this in the Bible. The closest thing is when Boaz called the elders of the city as witnesses to the fact that he agreed to take Ruth to wife when he completed a transaction to redeem a kinsman's inheritance.
Hebrews would marry by the groom or his father paying the bride's father a bride price-- if she were a virgin-- and later throwing a party. The groom would take her into his home. Later they had some kind of betrothal cup they drank from and a contract and dowry for the woman, but these are extra-biblical Jewish customs.
The pagan Romans had a custom where the bride and groom stood before a pagan priest who officiated and said certain words. The bride's words would be something like, "Where you are Gaius, I am Gaia.' Girls had the feminine version of their father's name at first, then a feminine version of their husband's name in Roman culture.
Skip forward 500 years into Christianity and it becomes church practice to have a church elder perform a similar ceremony. After the Reformation, Roman Catholics started to count marriage as a sacrament.
If an ordained minister chooses to perform ceremonies-- and serve a societal role-- it is up to him whether he wants to do this for unbelievers. Doing so may provide an opportunity to preach the gospel to them and give them some marriage counseling as to what marriage should be. It is not sin for two sinners to marry if they do it right. The same ordained minister could refuse to marry on the second go-round if they divorce.