Succession Certificate

My younger brother died. In his family there are 2 children alongwith wife now. Apart from this our mother is alive and myself as elder brother. Can his wife obtain Succession Certificate on her own without taking our signatures or consent? Can Court grant such certificate without taking our consent? Should we not given the copy of this certificate by Court? The wife of my younger brother made his own brother as nominee in bank account after death of my younger brother. Is it allowed that his brother can be made nominee in bank account? Is it legally allowed? We are concerned about future of children and want to ensure that, the money left by my brother is used judiciously for the upbringing of children and used in well thought manner which we suspect that, will not be done. Knowing the wife of my Younger brother, we think she will misuse the money and we want to have control over by it by legal way so that, children's future is secured. The age of children is 10 years and 5 years respectively. Please enlighten me. Thanks.