Sisters family not returning the property on which loan is due

Dear Experts, my brother had mortgage the property to the bank since he has to study abroad in the year 1997 or 98, but due to financial inability to pay the dues on time 2005 ,bank has advised my mother and my sister since they are living on the property from past almost 30 years ,some should merge there assets in our property and they will make the fresh case ,only on paper property been transferred on my elder sisters name while she was alive died 2 months back, the complete EMI and rest loan paid by my brother ,now by sisters family is not returning the property please urgently help