Any person can apply for Aadhaar who should be a resident of India, non-resident Indian (NRI) or any foreign citizen residing in India. Aadhaar is not for granting citizenship, since it is meant for establishing unique identity even NRIs and foreign citizen residing in India can enjoy the benefits of Aadhaar.
But, everybody should undergo the verification process that was carried out by the UDAI. They must be physically present to give their demographic and biometric information at any Aadhaar enrollment centre in India that is authorized.
Individual at any age can apply for Aadhaar number. Any child whose age is lesser than 3 years will not require giving biometric information and at that situation the Aadhaar related to the child will be linked to the parents or guardian, However the child when he is of 5 years in age should give his/her biometric information.
The child from the age of 5 to 15 years who has enrolled for Aadhaar has to give again his/her biometric information when his/her age becomes 15 years. The biometric of every person will changes on the basis of age, so the re-registering process is necessary. A person biometric will vary differently. When he is a child and when he is an adult.