Is it permissible to propose to a girl who is engaged under duress, and does this fall under the Prophet’s prohibition of proposing when one's brother has already proposed?

It is not permissible for a Muslim to propose to a woman who has already received a proposal from another Muslim, unless the first suitor abandons his proposal or gives permission. This is based on the saying of the Prophet, peace be upon him: "A man must not propose over the proposal of his brother until the suitor before him abandons it or the suitor gives him permission."

Regarding the acceptance of a marriage proposal, for a virgin, the decision rests with her guardian. For a non-virgin, the decision rests with her. However, if the virgin dislikes the suitor and explicitly refuses him, or if she designates another suitable suitor, then her guardian's acceptance becomes invalid, and it is permissible for the one she designated to propose to her.

According to some Hanbalis, the guardian's acceptance is invalidated even if the virgin does not choose another suitor.

The preponderant opinion is that a mature virgin cannot be compelled by her guardian to marry someone she does not desire, and she has the right to take her case to court. They based this on the hadith: "A virgin should not be married until her permission is sought, and a non-virgin until she is consulted." Also, Ibn Taymiyyah stated that compelling a woman to marry someone she dislikes is contrary to fundamental principles and reason.