What is the ruling on children eating from their father's money if it is unlawful, and what should they do if he does not respond? And is it obligatory for them not to eat from it, even though they are students who do not work?

The children should advise their father and warn him of Allah’s punishment if he persists in his illicit earnings. As for the family eating from his illicit money, this needs to be examined. If the entirety of his livelihood comes from illicit sources, then it is not permissible for them to eat from it if they are capable of earning their own living. However, if he has both lawful and illicit money, and the illicit money is predominant, then many scholars prohibit eating from it, while others permit it.