Father divorced my mother 12 yrs ago, now claiming maintenance from me

I belong to Hindu religion. My father got exparte divorce from my mother 12 yrs ago and we didn't get any maintenance from him. He never maintained us and we were brought up by my maternal GrandFather and my father cruely treated my mother demanding money. Few days ago,my father issued a legal notice to me claiming financial assistance without mentioning my mother, my younger brother and divorce he got and his remarriage as well. I heard he remarried another women and have a six yrs old son. My mother, my younger brother lives with me. I am very much concerned why should I have to pay money to him who never took care three of us, in fact was cruel to my mother, got divorced, remarried and now after several years claiming money from me. Please let me know what step I need to take and how far his claim would stand in the forum he may approach.