Individuals, having/opening demat accounts, either, singly or jointly with one or two persons can make nomination. If the shares are held jointly, all the joint holders are required to sign the nomination form.
Irrespective of the fact whether securities are held singly or jointly, only one person can be nominated. In the event of the death of the sole BO or all the joint BOs, all rights in the securities held in the demat account will vest with the nominee.