Do the hero and heroine in a Christian romance both have to be Christians?
At the beginning of the novel? No.
By the end of the novel? Yes.
The Bible warns us against being equally yoked, and advises us that a threefold cord (man, woman, and God) is not easily broken. I take that advice to heart in life and in fiction. Just as I would counsel a friend against marrying an unbeliever, I wouldn’t like to see a fictional character make that mistake… unless it’s women’s fiction and the whole point of the book is to show the problems that come with marrying an unbeliever (but then it’s not a romance, is it?)
I have known people who have married unbelievers.
One was married with three children by the time we met. She was a strong Christian and was raising her children in the church, but she said it was difficult … especially when it came to tithing. She wanted to be able to contribute financially to the church, but her unbelieving husband (the family breadwinner) had a different view.
Another was a strong Christian who started dating an unbeliever who became a Christian while they were dating and before they married (or so they told us). We lost touch (due to living in different countries), but recently met up with them again. They are no longer Christians and aren’t raising their children in church.
So while I expect the hero and heroine to both be Christians by the end of the book, I actually prefer it if they are both Christians at the beginning. I’m always a little sceptical about the longevity of a relationship where one person is a new believer, as I can see it causing problems later in the relationship after the last page … and while some romance readers don’t mind the “happy for now” ending, I want to read “happily ever after”.