Is a girl's marriage contract valid Islamically in the absence of her father and the presence of her guardian brother, given the difficulty of communicating with the father who has neglected his children for many years?

The father has more right to marry off his daughter, and the brother has no guardianship over her while the father is alive. What was mentioned about the father's negligence does not negate his guardianship, as long as communication with him is possible. Therefore, the brother has no right to authorize his maternal uncle to marry her off, and this marriage is void and must be annulled, and the contract renewed in the prescribed manner. The child resulting from this marriage is attributed to his father due to shubha (resemblance/doubt).

The father must fulfill the rights of his children, and whoever neglects this is sinful. And a Muslim must ask the people of knowledge about what he needs regarding his religious matters before taking action.