(one's) next of kin
One's closest living relative. Now that the body has been identified, we'll have to notify his next of kin of his death. The will specifies that her next of kin will be entitled to her entire estate.
one's next of kin
one's closest living relative or relatives. The police notified the dead man's next of kin. My next of kin lives 800 miles away.
your ˌnext of ˈkin
(formal) your closest living relative or relatives: The hospital need to contact her next of kin — she is very ill indeed.This form must be signed by your next of kin. Kin is an old word for your family or your relatives.