Stopping my father to sell the property

Hi! I am Mukesh presently residing in Delhi. First of all I need to explain my story. My father first marriage whom I called Badi maa (she was polio affected and handicapped that's why she don't have any child and my father don't stay with her)and I use to live with her and now she is no more. My father has got some agricultural land and house on her name. Second marriage with my mom unfortunately she also died when I was just 2 and half years old. I was brought up by my badi maa parents ie Nana nani in Ranchi. After my mother's death my father married third time and my step mother is not good that's why I have to live with my badi maa. Due to my step mothers influence my father started disliking me. He only doing formality to me by sending money for my studies. I have one sister and one brother from my step mother and they too because of property issue donot like me or talk to me. Actually they all do not want to give any share in the property and they sell something behind my back without my knowledge. Now my father cannot walk due to problem in his legs and I hardly go to him as I and my wife donot get any respect from them. sister fell down from college building so she also became handicapped. Brother finished engineering from chennai but he has an eye in property so he lives with parents only and do not do any job but doing some business at home only. Now I want to ask following points:_ 1. Now they are planning to sell my grandfather s property. Can I stop them from doing so? 2. If any property is on my badi maa name purchased by my father and she is dead. My father can sell that particular property without my consent? Can I stop him from selling? 3. Any property on my step mothers name. Can I get share on that property legally?