What is the ruling on dealing with money acquired by a brother through stealing credit cards online, and is it permissible to eat from it or borrow it, and what must the brother do if he repents to return this money to its unknown owners?

If your brother's only money is from stolen cards, then neither you nor your father are permitted to benefit from it or borrow from it. This is because it constitutes cooperation in sin and consuming others' property unlawfully. If you know its circumstances, you must return the money to its owner or give it as charity on their behalf if reaching them is impossible. However, if your brother's lawful money is mixed with unlawful money, and he has a permissible income, then dealing with him is permissible, especially if the lawful portion is dominant. You must advise your brother to abandon this act and return the stolen money to its owners, or give it as charity on their behalf if he cannot reach them.