A Foundling Has Been Raised by a Family for Twenty-one Years. There Are Questions - Jurisprudential Answers - Miscellaneous Issues, Vol 1

Ahmed al-Hasan Response:

A foundling is not judged to be a child born of adultery unless that is established by valid religious evidence. Rather, a foundling is considered a person whose father and lineage are unknown. No one may attribute him to himself, and such an attribution would not be valid. If the foundling is a believer, he is your brother in religion. The believing community must deal with him as a person of unknown lineage, not as an illegitimate child, and anyone who treats him as an illegitimate child commits a sin. As for this particular person, he should be encouraged to pray and fast, and before that to believe and show loyalty to the wali of God. A wife should be sought for him who accepts his condition as a person of unknown lineage. God is the Giver of success.