Does the rule of "choosing the lesser of two evils" apply in a case where a father owns shares in a usurious bank and refuses to dispose of them, with his son offering to buy them from him with money for his marriage, knowing that benefiting from ill-gotten gains is impermissible, and what are the alternative solutions if the rule does not apply?

It is obligatory for the father to listen to the advice of his children, and it is obligatory for the son to continue advising his father with gentleness, wisdom, and good manners; because that is more conducive to the acceptance of advice. Indeed, the father's participation in usurious banks is forbidden by scholarly consensus, and it is obligatory for the father to return these shares to the entity from which he bought them, because the contract of their purchase is void. If the bank accepts the return of its shares, then praise be to Allah. If it does not accept, it is not permissible to sell them to anyone else. If the bank reclaims its shares, it is not permissible for the father to receive more than the money he paid, and he must dispose of the excess money by spending it on charitable causes and for the benefit of Muslims.