Is it obligatory for fathers to provide for their children born out of wedlock before their conversion to Islam, given that there was no legal contract between them and the mothers?

If intercourse occurred during disbelief, and the spouses believed the marriage contract to be valid, then the children belong to the man. The contract does not need to be renewed after conversion to Islam, unless the woman is not permissible for the man according to Islamic law. However, if the intercourse was with the intention of zina (fornication), then the children are considered the man's children if he acknowledged them as his during disbelief and there was no one contesting their lineage. The obligation of maintenance for the children arises from the ruling that they are the man's legitimate children.