This definition appears very rarely
See other meanings of PNOK
Samples in periodicals archive:
Because DOMA defines marriage for federal purposes as "between one man and one woman," same-sex military couples cannot qualify for many protections available to other couples, including health care, housing assistance, primary next of kin status and survivor's benefits.
The announcements are made on the Web site no earlier than 24 hours after notification of the service member's primary next of kin," it explained.
Another recent reform is the assignment of casualty officers to assist not only the primary next of kin, but to also help other relatives.