All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The scholars differed in opinion with regard to marrying an adulteress/or fornicator. The most preponderant opinion, however, is that it is forbidden to get married to her unless the following two conditions are met:
1. She has to repent from committing adultery or fornication.
2. To deliver the baby.
However, since this marriage has taken place, then this woman becomes the wife of this man according to the opinion of those few scholars who consider that this marriage is valid.
Since this woman is now married and has a husband, it is not permissible to marry her off to another man even if it is the person with whom she had fornicated, as he has no right in her.
Finally, we draw your attention to the following matters:
1) The two fornicators must repent and be careful from anything that might lead them to committing adultery/fornication again.
2) The child from fornication has to be traced back to his mother and cannot be traced to the person who married her or to the person she committed fornication with.
Allaah knows best.