Parents divorced how to claim share in father's property

My father died 2 days back.my father and mother got separated before 30 years.I am with my father,sister with mother.now tell me how they divide the property,since there is no will.one of my friends told If both father and mother are separated for more than 22 years it is naturally divorced. Is there any option found like that.If my Mother and sister says we don't want that property,then what should be done,do I have to get a docment from them stating that they are willing to give me.If I get also is there any chance that they can come for a claim during later years.kindly advise