Registered gpa

Hi I am Deepak we are 3 brothers & 1 sister from Delhi my father bought property on GPA on 2005-06 in south Delhi, caught with cancer where none of siblings came front to support financial for his treatment except me hence my father transferred Registered GPA to me Jan 2014 & all papers were lying with him.Now my brothers forcefully taken from him and took him to make another GPA and will without my knowledge and my absence Aug 2014 with witness one of my cousin and 1 neighbour. Now they are holding original documents of mine, father died in 2016 they took possession their own choice... I have tried to register FIR where they have used their influence hence no FIR registered, after which I have send 3-4 complaints to DCP & SSP south but no action till today; they are freely enjoying also filed case in court for permanent injunction sec 73, on their own papers made which was not registered at all. Suggest what to do I am in debt as took money on interest from some known people for my father treatment.