Source: As worded by Indian Railways, Government of India

If you are holding a confirmed ticket and are unable to travel, your ticket can be transferred to your family members viz., father, mother, brother, sister, son, daughter, husband or wife. To transfer your ticket, you must submit your request at least 24 hours in advance of the scheduled departure of the train.

Tickets which can also be transferred

1. To another Government Servant traveling on duty, at least 24 hours in advance of the scheduled departure of the train.
2. To other students of recognized Educational Institution when the Principal/Head makes a request at least 48 hours in advance of the scheduled departure of the train.
3. To other members of the marriage party, if the head of such a party makes a request at least 48 hours in advance of the scheduled departure of the train.
4. To other cadets of NCC, if the head of the group makes a request at least 24 hours in advance of the scheduled departure of the train. Such changes can be made only once - if the request does not exceed 10% of the total number of group members.