Property Inheritance

My dad has brother who is unmarried and expired and one sister who got married also expired ... She has a daughter who also expired leaving behind three children. We are 6 children. Since uncle is unmarried. There is no one to inherit in Class 1 heirs. My Dad and mother have expired. How do we claim his inheritance. We want to put our names in his property. We also have a will from him before his death that his immovable properties will be for his brothers children but in that Will there is no details of the property numbers. This will is signed 30 years back in presence of the witnesses with thumb impressions. We went to the city survey officer and he says the property number is not mentioned in the Will. Unmarried uncle >> Sister ( expired ) >> Daughter (expired) >> the three children are trying to also claim in this property. Pls help me how to claim our rights in this property as currenty there is a small room in this property and they pay rent of Rs 100/- since 50 years and now we need to settle this property issue and they have stopped paying us rent since two years.