What is the ruling on the actions of the second wife's children regarding their father's property, as he suffers from Alzheimer's, and their neglect of him, and what should the children of the deceased wife do in this regard?

If a man is afflicted with dementia and cannot manage his wealth properly, then his children have the right to object to their siblings' improper handling of his money. It is legislated for them to bring his case before a judge to interdict him and appoint a trustee over his wealth. It is preferable for this to be done by mutual consent without resorting to the judiciary.