Is it permissible for the current husband to attribute the daughter to himself after her father and his family have abandoned her, knowing that she is his biological daughter, and what is the stance regarding her paternal siblings, and should she be informed of the truth when she grows up, and what is the solution to avoid future trauma for her, taking into consideration that registering her as "father unknown" might cause her shame and disgrace?

Islam has forbidden adoption by the text of the Quran. An adoptive father of a girl must disown her publicly and before his children to avoid legal prohibitions. There is no objection to gradually informing the girl of the truth: that her real father is the one who married her mother before the man she believed to be her father. "The child is for the bed"; thus, the establishment of lineage does not depend on the validity of the marriage as long as the husband believed it to be valid.