If the property was on your father's name and he is reported to have died at Bangalore as well as the property is situated in Bangalore, then you have to get a legal heirship certificate in respect of the legal heirs of your father at Bangalore only ,
The family tree certificate issued by Tehsildar at Telangana may not be considered as legally valid document to transfer the property revenue records/khata to your names from your deceased father's name.
However the family tree certificate issued by Telangana state may come to your rescue to obtain legal heirship certificate form Bangalore.
After that all of you can jointly execute the registered sale deed in favor of the prospective buyer