How can a army mans recover his dues after his death

My brother  was in army (FD regt -65, artillery ).He was posted lekhnagar Nasik . He came from nasik on date 25-06-2016 and found dead in Meerut. He was murdered by proof ,evident and postmortem report. He was married on 22-02-2016 to XYZ .After his murdered his wife left his home and has contracted remarriage with another person but by now she has not done remarriage. We have contract with XYZ  on stamp paper in written and pay her alimony . On stamp she clearly mention that she will remarriage with another person. In the army records ABC mother is nominee and no evidence there about his marriage life. Now his wife demands his dues , pention etc. and his mother who is nominee there demands also . Plz advise us what should we do in this case and which will be given his dues and pention etc either mother(nominee) or his wife. We want to know about this what is the regulations in this type of cases. We want his dues for his mother early .