Legal heir and succession certificate

Dear Sir/Madam, 2 months ago my jijaji passed away due to covid and he is survived by wife (my didi) and son. Now when we are seeing at most of the banks nomination is not mentioned and at some places nomination mentioned is his mother (means mother-in-law of my sister). Now her mother-in-law also not alive. So she has to get Legal Heir certificate from SDM. We applied once where laywer suggested to put only her name in application of legal heir. But application got rejected saying, application should also mention father-in-law and son in application. Her father-in-law is very supportive and saying he dont want to be their in legal Heir certificate and ready to sign NOC that he agrees the property and bank savings should be given to her (my sister). Is it possible to put only her (my sister) name in legal heir certificate if we provide NOC or any affidavit. Because her father-in-law dont want to be present on all documents sign in future also. Kindly provide me legal advice for the same, it would be very helpful for my sister. Thanks & Regards Sandeep Rawat