If no guardian has been appointed pursuant to N.J.S. 3B:12-13 and N.J.S. 3B:12-14, or if the surviving parent was so appointed, the surviving parent may, by his will, appoint a guardian of the person and a guardian of the estate, or a guardian of the person and estate, of any of the parent's children, including children en ventre sa mere, who are under the age of 18 years and unmarried at the death of the surviving parent.
N.J.S. § 3B:12-15