Is a marriage valid if the brother fails to attend the عقد (marriage contract) or refuses to, knowing that he is the شرعي (legal) guardian of the girl whose father has passed away, and he does not provide for her?

For a marriage contract to be valid, it must be solemnized by the woman's guardian (wali) or his agent, in the presence of two witnesses, based on the Prophet's (peace be upon him) sayings: "There is no marriage except with a guardian" and "There is no marriage except with a guardian and two just witnesses." This condition is not waived due to the guardian's negligence or existing disputes between him and the woman under his guardianship. If the brother attends in person or appoints someone else for the contract, that is what is required. If the guardian refuses to marry off his sister without a valid Sharia-compliant reason, the girl may refer her case to a judge, who will then perform the marriage, or the guardianship may transfer to the next in rank among the guardians.