Is it permissible for children to demand from their father, who covered the wedding expenses of his eldest son but refused to cover the weddings of his other children who are less financially able, the same amount he spent on their eldest brother?

Wedding expenses covered by gifts and donations, the preponderant opinion is that it is obligatory to equalize among children in this matter. Therefore, it is not permissible for a father to allocate wedding expenses to one child without his siblings, and the children have the right to demand equalization. The father should give everyone the same amount he gave to one of them. It is obligatory to honor one's parents and treat them kindly, and their right is not forfeited by their injustice towards some of their children.