How does a man married to two women justly divide expenses between his wives, given the difference in the number and ages of their children?

Justice between wives regarding expenditure is achieved by providing each wife with her needs of food, clothing, and shelter, according to what is customary. As for the children's expenses, they are obligatory upon their father as long as they are in need, and this has no relation to justice between wives. It is not just for the husband to equalize the expenses of a wife with her three children with the expenses of another wife and her infant child. Rather, he should spend on each wife sufficiently and spend on his children according to what is customary. Sheikh Ibn Jibreen mentioned that the husband gives wives according to their needs, and gives children according to their needs. For children, their expenditure is considered expenditure for relatives, while for wives, their expenditure is considered expenditure for exchange. He equalizes between wives in the expenditure that pertains to them. As for the mother of children, he gives her the expenses for her children, and the one who has no children does not demand the same.