property dispute

Dear sir/madam . My father purchased a Tamilnadu Housing Board Property from a person who was allotted the home on 1984. My father purchased from him the home from him on 1992.that time they made a entire payment and a sale deed was made which was unregistered. My father and the party made a sale agreement. In which all terms are mentioned including the pending payment to be made to the TNHB on EMI Basis. By 2001 the two parties made a POA which gives full power to my father to do anything on property.mean time my father made all payments to TNHB.So my father approached TNHB. For PUCCA SALE DEED he learnt TNHB hiked the rates and only when the full payment will be done thr sale deed will be executed between the TNHB & Allottee. After a long legal battle TNHB finalised the final payment and sent notice. Unfortunately before making payment my father expired .and now the actual allotee demanding more money from us to get registration. And unfortunately the home is occupied by younger brother who is ready to cheat me in this matter and he stays in home without paying rent or any compensation to me. And for the last 6 years the matter is unsettled. I dont get clear picture how to move ahead in this matter since my siblings are not cooperative. I have invested money in Home. While the construction. Now my questions are 1 1) Whether I can register the property in my name from the consent of allottee? 2) if my siblings are hurdle for the registration. What should I do? 3) When full payment was made at the time of purchase If the allottee ask extra money I have to pay or not? 4) If my siblings are not cooperative in settlement for registration what should I do further? Pls suggest me what should I do Regards S.Kumar