Is what the father did—spending most of the mother's inheritance on the daughters' dowries and marriages after her death, then withholding the remaining inheritance—lawful or unlawful? And must the children from the new wife inherit from this inheritance, and what is the amount due to them?

A father is not obligated to equip his daughter from his own money. Rather, he should equip her from her mahr (dowry) if there is one, or from her own money with her consent if she is an adult and mature. If the father disposed of the mother's inheritance with the children's consent after they reached adulthood and maturity, then they do not have the right to claim its value after the father's death. You must return the money you took from your father's estate by adding it to the rest of the estate and re-dividing it, along with adding the father's share of the mother's inheritance, which is one-fourth. We emphasize the seriousness of inheritance matters and the necessity of presenting them to Sharia courts.