Is my marriage Islamically valid to a woman whose brother agreed to her marriage, while her father is in another country and did not attend the عقد (marriage contract), and is it permissible to consider the brother a guardian in this case?

The jurists differed on the condition of the guardian (wali) for the validity of marriage. The majority (Malikis, Shafi'is, Hanbalis) stipulated it, while the Hanafis did not. A marriage contracted without a guardian is invalid according to the majority, and it must be annulled and a new contract made in the presence of the guardian or his representative. The brother's consent is not considered sufficient by the Shafi'is and Hanbalis if the father is present, whereas his guardianship is valid with the Malikis and Hanafis under certain conditions. The brother's guardianship is generally valid when the father's guardianship is impossible or he is absent.