First of all you should do some inquiry about the name of nominees in the pension papers of your father. If your name has been mentioned therein as a nominee then you are entitled to get 50% of family pension until you attain a certain age. In this situation your mother is not entitled to receive the entire pension.
If your name has not been mentioned in the pension papers as a nominee then you should move a representation to the head of the department and demand to disburse the pension between the son and widow of the deceased pensioner.
In that representation you should enclose a copy of the family register, death certificate of your father and your age certificate. A minor son is also entitled to get a certain share in family pension because he is also a dependent. The dependent son is entitled to avail retirement benefits of pensioner.
In Soumen Kumar Mondal v. Union of India, 2016 SCC OnLine Cal 2216 the Calcutta High Court has held that a minor son will continue to draw 50% of the family pension till he attains the age of 25 years. Thereafter the widow would be entitled to the entire amount of the family pension.
Therefore, distribution of family pension between minor son and widow is possible if the son is minor and not able to maintain himself.