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.
The scholars differed in opinion on whether the presence and consent of the Wali (guardian of the bride) is a condition for the validity of marriage, and the majority of the scholars are of the view that the guardian is a condition and that the marriage contract is void without him. However, Imaam Abu Haneefah held that a woman has the right to marry herself off (without a guardian) and that the marriage is valid in this case. We, at Islamweb, adopt the view of the majority of the scholars, and we consider it to be the preponderant view. Please refer to fatwa 83629.
However, if the marriage was not based on either of the above options, then it is a void marriage and must be annulled; and the marriage contract can be renewed fulfilling the conditions of a valid marriage.
With regard to the baby, it is his child in any case. If we presume that the marriage was valid, then the matter is clear. If we presume that the marriage was not valid, then the child is still attributed to him because he married her while believing that the marriage was valid. For more benefit, please refer to fatwa 231757.
We advise you to be patient in order to solve the matter in a wise manner. You may seek the help of some rational people among the relatives in order to consult them and for everyone to cooperate in dealing with any effects that might result of this case.
Your parents as well as your whole family should not blow the case out of proportion, and they should praise Allaah that it was not a case of pure adultery, as the marriage is considered valid according to one of the reliable and major Mathhabs of Ahlus-Sunnah (Hanafi).
It should also be pointed out that marriage among relatives is not forbidden in Islam, and being too strict about this may lead to such situations, so the parents should be aware of this. Please, refer to fatwa 31254.
It should also be pointed out that the consent and presence of the guardian is a condition for the validity of the marriage, regardless of whether the parents are alive or dead.
To learn the order of guardians in marriage, please refer to fatwa 83338.
Allaah knows best.