Is the money earned by the father through unlawful means, by feigning illness to receive a salary without working, considered illicit (haram), and is it permissible for the son to partake of this money?

What the father takes from money allocated to a specific group, while he is not from them, is impermissible for him to take, and it is haram (definition) (forbidden). It is not permissible for the son to accept this haram money except in cases of necessity to obtain food, clothing, and shelter if he is unable to obtain these through his halal (definition) (lawful) money. If the father has halal money from which he spends, then there is no harm. If halal and haram money are mixed and indistinguishable, then it is disliked for the son to take it, but not forbidden.