Is it permissible to conduct a DNA test to confirm the lineage of a nephew who exhibits signs of physical and behavioral differences, raising suspicions that he may have been replaced with another baby at birth in the hospital?

Doubts and misgivings about lineage should be ignored, as a difference in resemblance does not negate lineage. It has been reported from the Prophet (peace be upon him) that a difference in color does not negate lineage, and that a child may resemble an ancestor. Mistreating the mother and sisters does not affect lineage, and it is impermissible to deny a legally established lineage based on modern medical means or by conducting a DNA test to confirm it. Furthermore, the Islamic Fiqh Academy prohibits relying on DNA fingerprinting to deny lineage or using it to confirm the validity of legally established lineages. It also recommends prohibiting private entities from conducting these tests except upon a judicial request.