Does it affect the validity of the marriage contract if the groom's representative in the contract is the uncle instead of the brother, and without an explicit authorization from the groom?

The jurists differed on the issue of an agent appointing another agent (sub-agent). The majority of scholars held that an agent is not permitted to appoint another agent unless authorized by the principal, because the principal approved of the first agent and not of anyone else.

The Hanafis, however, permitted an agent to appoint another agent if the first agent was present at the contracting session with the one he appointed, because the intent is the presence of the opinion of the first agent, and this has been achieved.

The Malikis held that an agent is prohibited from appointing another agent unless the agent is not fit to perform the task himself, or the work is extensive and requires someone to share it.

The Hanbalis held that an agent is not permitted to appoint another agent unless authorized by the principal, or if the principal said to him: "Do as you wish" or "Act as you wish."

Therefore, the contract must be renewed either by the agent directly conducting the contract himself, or by the principal authorizing him to appoint whomever he wishes.