Fraudulent registration of property.

Sir, Our father owned an ancestral property in the village In Gurugram District of Haryana State.. He died intestate over forty years back. We are five brothers and a sister who are legal inheritors of the said property. All are married and over fifty now. We five brothers had fought a legal case also together between the years 2000 and 2003 in a Gurugram Court relating to the way of access to the property with the neighour (who had filed the case), wherein all the five brothers had admitted that the property belonged to all of us jointly. However, one of our brothers has got the property registered in his name fraudulently without my knowledge or consent. I have no documentary evidence with me except saying that the property is ancestral and that all the five brothers had admitted the joint ownership over the said property in that case. In such circumstances, Sir, can you advise,- 1) what can I do now? 2) what are the remedies? 3) what documents will be required to file a court case in the present case? 4) how the documents can be procured and from which source? 5) in case some of the documents are desired to be obtained through RTI from tehsil office, what input shall be required to be produced to the tehsil? 6) which documents can be obtained from the tehsil office through RTI? 6) In case I desire to file a police complaint, can I do so, and submitting which proofs? Kindly solve the questions pointwise. I Shall be very thankful.