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.
We have already issued Fataawa 88415 and 86418 clarifying that adoption is forbidden in Islam. Therefore, your brother adopting your daughter and preventing her from seeing her mother and relatives is a great evil and an abominable sin. Although the Sharee’ah did not specify a punishment for adoption, the fact remains that its sin is grave since it leads to the loss of people’s rights, the falsification of the reality, and violating Allaah’s prohibitions. Hence, you should invalidate this adoption and correct the papers by tracing back the daughter to her real father.
Allaah Knows best.