Brother died in accident,police not acknowledging complaint what to do

My brother met with an accident at Chennai. He went in a two wheeler Honda Activa. Opposite party with his wife and two minor children went before him in a bike. My brother got serious injury and opposite party not allowed to take him hospital until police came to the spot for an hour. Further, opposite party made FIR on very next day knowing the condition of my brother stating that when he was parking the vehicle on the left side of the road, my brother dashed his vehicle.FIR section 279 & 337.My brother died in the hospital after 4 daysl..After 15 days we gave complaint local police station but not acknowledged.Then copy filed before DCP. Based on that enquiry was made but allegation made by us has been removed by getting letter from us. Now, what to do further. My brother aged 46, B.E., Manager in a company earnings ctc 1 lakh per month. I expect a legal opinion from a senior lawyer.Kindly advise.