Pension

My maternal grand father passed away. He has three daughters including my mother..my two khala,s are not processing his pension case. .they are not signing his pension documents. the reason is they know my mother will get his pension since she is widow and by law she is entitled to get his pension.. its been 5 months and they are not providing us pension documents. What shall we do? shall we go to court? my mother will get pension as per law. But AG office us saying all of them have to submit documents. kindly guide