Is it permissible for children to file a lawsuit against their father who discriminates in how he treats his children and deprives some of them of their legitimate rights?

If the father does not violate the rights of his wife and children and maintains justice between his two wives and children, then it is necessary to continue advising him gently and reminding him of the Prophet’s saying: "Whoever has two wives and inclines to one of them over the other, will come on the Day of Resurrection with half of his body leaning." Also, remind him of the hadith of Nu'man ibn Bashir concerning the rejection of a gift in which there was no justice. A void gift is not effective if he gave to some children without others. As for his actions of buying and selling and other transactions, they are valid as long as he is competent to act and within the bounds of Islamic law. Upon his death, everything he gifted to some children or to his wife returns to the estate to be distributed among all heirs. The son is advised to fear Allah, treat his father kindly, and be gentle with him.