North Carolina statute 31-9 Executor competent witness.
No person, on account of being an executor of a will, shall be incompetent to be admitted a witness to prove the execution of such will, or to prove the validity or invalidity thereof.
However, it still requires two witnesses per 31-3.3 Attested written will.(a) An attested written will is a written will signed by the testator and attested by at least two competent witnesses as provided by this section.
However, in the long run it's probably a bad idea because even a hint of impropriety could result in an expensive and time consuming lawsuit contesting the will.
Best to get the will maker to have two independent witnesses.
Better yet, have the will maker do a self-proving will. See statute 31-11.6: