As a general question: If a couple became attached through a haram relationship and later wish to marry, but there are doubts that such behavior could continue after marriage and it is unclear whether sincere repentance has occurred, how do scholars advise viewing such a situation?

Maybe you can anonymously send this on the form on Tuesday, because I do not understand the question. Do you mean it is out of wedlock, or do you mean that, intimately, as a husband and wife, you're actually doing something that is forbidden? I need to know so that I know how to answer.