Post office pension

Hello.My father expired a year before.He is a subpostmaster in post office.His 1st wife died due to breast cancer.He has 5 children whose age is in between 35-50 who are married as well.My father married my mom after a year of his first wife.My parents got married in a church and the marriage is not registered legally by the church pastor as he died before the my mom’s name is not mentioned in the family pension book though their couple photo is attached in it.later they got registered their marriage and due to my father’s health condition he didnt completed the family pension process.And my mom was never married before my dad to complete the pension process it needs a family certificate which we cannot get because it needs the signatures of my father’s first wife children as two of them refused to sign for the certificate.its almost 15 months from my father’s mom is not financially independent and i am still can you please tell us what do we do now.Thankyou.