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.
Fornication/adultery is one of the major sins. Whoever commits this sin must repent sincerely without any delay. See our Fataawa: 84637 and 88978.
Abortion is forbidden even if the pregnancy was due to illegal sexual intercourse. It is another sin in addition to the sin of adultery. See our Fatwa: 83114.
Finally, marrying a person who has committed illegal sexual intercourse is not allowed unless he/she makes sincere repentance as we mentioned in our Fataawa: 83176 and 83680.
As for the lineage of the child who was born without valid marriage read the Fatwa: 84788.
Allaah knows best.