share of my father in the property of my grandfather

Hello sir, i am Rishabh jain son of kamlesh jain, sir i need advice relating to share of my father in the property of my grandfather. sir, my father have four brother and two sister, my grandfather has land in the rajasthan and he has constructed house on that land in back 1980 and and there is no purchase deed or any other document relating to such land or from whom the land has been purchase and also there is no will written or registered by my grand father. After death of my grand father my grandmother is leaving with the younger brother of my father, so the younger brother is claiming that property as his property and he want to demolish that house and want to build a new house on that land without giving share to my father and elder brother of my father are also are with him. younger brother has also paid 120000 to each of them without giving any information to us relating to this. we have kept our all stuff in that house and whenever my father visit rajasthan younger brother gives us thereat of throwing all our stuff on road side. please help us .