Is a girl’s marriage, conducted by her maternal uncle acting as an agent for her brother—there being no other male agnate (wali ʿaṣabah)—valid, and must the marriage contract be re-formulated when her brother is present?

It is permissible for the guardian to delegate another person to conduct the marriage contract for his female ward, whether this person is a relative or a stranger. This is because marriage is a contract of exchange, and delegation is permissible in it, just like in a sale. The Prophet, peace and blessings be upon him, delegated Abu Rafi' to marry him to Maymunah, and 'Amr ibn Umayyah to marry him to Umm Habibah. Thus, marriage is concluded by the offer (ijab) from the guardian or his representative and the acceptance (qabul) from the husband or his representative, and in the presence of two just witnesses. Therefore, the contract conducted by the maternal uncle on behalf of the brother is valid.