The usual answer given the believer is from 2 Corinthians: Do not be bound together [unequally yoked] with unbelievers; for what partnership have righteousness and lawlessness, or what fellowship has light with darkness?( In these verses, the Apostle Paul compares believers with unbelievers in terms of light with darkness (verse 14), Christ with Belial (a references to Satan, verse 15), a believer with an unbeliever (verse 15), and a temple of God with a temple of idols (verse 16). Even though you may think you have a lot in common, the most important things you don't hold in common.
I took the long view that you can’t predict what’s going to happen.Usually, by the time the question is asked, the relationship has gone far enough that a negative answer is going to be difficult to accept, even if it is the right answer.The short answer is "no." However, it is good to examine the scripture behind the answer to understand it more completely, including why such a marriage is a bad idea.He would now quite happily call himself a Christian and a believer.Of course, there are no guarantees on that front and I don’t think you should ever go into marriage hoping to change the other person.