What is the ruling on the children agreeing to divide their father's real estate income equally between the children of each wife, given that one of the sons mortgaged the residential villa and personally benefited from the proceeds of the mortgage?

Your agreement to divide the income from your father's properties is not permissible. His ownership of all his wealth remains as long as he is alive, even if he has lost his memory. His property is under interdiction, meaning he cannot dispose of it through selling, buying, or gifting. Rather, his guardian should spend from it on his affairs and needs, such as medical treatment, and on obligatory expenses, such as his minor children and wife. The matter must be brought before a شرعي judge to consider the issue of this wealth and what was spent from it unlawfully, as well as the matter of the mortgaged villa, and to appoint a guardian to oversee the interdiction of the property and its disposal.