A witness to a will should be an adult who has full capacity for civil conduct and can understand the contents of the will. Have no interest relationship with the heir or testator. Because people with interests are more likely to be driven by interests and make untrue proofs. Therefore, heirs can't be witnesses, and creditors and debtors of heirs and legatees, as well as partners in the same business, should also be regarded as interested in heirs and legatees and can't be witnesses of wills.
Legal basis: Article 135 of the Civil Code of People's Republic of China (PRC).
A will that entrusts others to write on behalf of others shall be witnessed by two or more witnesses, and one of them shall write on behalf of others, which shall be signed by the testator, agent and other witnesses, and marked with the year, month and day.
Article 140
The following persons cannot be witnesses to the will:
(1) Persons without civil capacity, persons with limited civil capacity and other persons without witness capacity;
(2) Heirs and legatees;
(3) People who have an interest in the heirs and legatees.