It shall be illegal for any superintendent, principal or other licensed employee to be elected by the school board if such superintendent, principal or licensed employee is related within the third degree by blood or marriage according to the common law to a majority of the members of the school board. No member of the school board shall vote for any person as a superintendent, principal or licensed employee who is related to him within the third degree by blood or marriage or who is dependent upon him in a financial way. Any contract entered into in violation of the provisions of this section shall be null and void.