As far as I understand, the name of the unmarried daughter can be added for the purposes of the family pension only after the death of the wife of the pensioner, who is at present getting the family pension. Only at that time, it can be ascertained whether the daughter is still unmarried, what is her age, what is her income and whether other conditions, if any (as per the Rules of the concerned Government) are satisfied by the daughter.
Please note the difference in family pension being given to the wife of the retired Government servant and to the unmarried daughter. In the latter case, there are certain conditions that are required to be satisfied which can generally be tested only when the time is ripe to consider the applicability of those conditions.
However, you may make enquiries with the concerned department which is paying pension to your mother for a more accurate answer to your question.
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