My sold his in undivided property illegally

We are 3 brother and 3 sisters owner of undivided anstral property. On that property me and my brother is only living in a building. Half of the building he is living half of the building I am leaving other people are live in Mumbai and Pune. my 1 brother and 2 sister had sold their share in undivided property without asking me and others. In purchase deed they have mentioned that our property is open land but in reality on our land there is a building . They have mentioned open land in purchase deed because they want to save their stamp duty. There is 3 person who have purchased. Letter on one of them has sold his share to another third person and in that purchase deed they have mentioned that there is one small room and shed house. Our property is instral property and that third person is saying that he wants to demolish his side of property . there is some temporary compound between 2 houses but both houses are so connected to each other that they are a single building , third person who have buy his share he is telling that he will demolish his side of building but if they do that our building will also collapse Our building is nearly 80 years old but our side part of building is in good condition because from time to time we have done maintenance work on that but on that side of area on which my brother is residing is in bad condition because they were not reluctant to spend money on building please tell can I stop them from demolition their side of building?? because no demarcation and partition of the property has done can that third person apply for partition and demarcation?? If I go to court I have to paid stamp duty for filing the case after filing the case third party and buyer will ask the court for partition without filing any stamp duty it is disadvantages to me because I have to pay stamp duty without my mistake can they do that?? If court order that the entire transaction is void then will that 1 brother and 2 sisters name will also be again mention in property document 7/12 or what kind of order Court can give in this case??. In how many days Court can give the stay order for demolishing the building