What is the ruling on a son taking his salary from his father's money to pay off his father's debt without his knowledge, and is the sister sinful for keeping the money with her?

If the father acknowledges his son's right to the salary but is in financial difficulty, it is not permissible for the son to take the money without his father's knowledge. It would have been more appropriate for the son to assist his father in his difficult circumstances. The father has the right to take his son's money if he is in need. The son erred by taking the money without his father's knowledge, and the sister erred by agreeing to hold onto the money. If the father's financial difficulty ceases and he procrastinates while being able to pay, then it is permissible for the son to take his right without his father's knowledge. However, before that, the son must return what he took in a way that the father does not perceive. The children should repent to Allah.