According to LegalZoom.com, the term "next of kin" refers to a person's closest surviving family member. When a person dies without a will, the next of kin, as determined by laws of intestate succession, inherits the estate.
A married person's next of kin is his spouse. If a person is not married but has children, his children are his next of kin. If a person is not married and does not have children, his next of kin are his parents, followed by his grandparents or his siblings. If a person dies with no living relatives, his estate is conveyed to the state treasury. Next of kin determinations can vary from state to state, according to LegalZoom.com.