What is the ruling on supplicating against an unjust father who does not fear God, takes his children's money, lies to them, spends it on his second wife, separates his children, and curses his wife and children?

If the father is abusive, that does not negate the obligation to honor him and treat him well, nor is it permissible to supplicate against him. Children must be taught not to belittle their father.

Among the greatest acts of kindness towards a father is to supplicate for his guidance and to strive for his reform through advice or by bringing virtuous people to influence him.

As for siblings, one should respect them, show concern and compassion towards them, and use indirect means of advice, such as playing influential lectures.