Rights of Mentally ill son on property?

I have 3 brothers. None of them work and are all fully dependent on my father's income. My father has good wealth. My eldest brother is a lawyer and was earning few months back. But suddenly, he got mentally unstable and now he's under treatment. My father denies his illness and treats him really poor due to influence of my other 2 brothers. He insults him in front of everyone. Pushes him away. My brother have his wife and 3 children and they're being humiliated everyday by this behavior of my father. My father is also denying any financial help and providing everything to other two sons. What actions can I take against my father and other brothers? Also what are the rights of a mentally ill person over their parent's property?