When a request of a county governing body or a petition as prescribed in § 4-5-120 has been presented to the Governor for changing the boundary line or lines between two counties, whereby a portion of the territory of one county would be annexed to another, the Governor shall within thirty days appoint a commission of four persons, two from the territory proposed to be annexed and two from the other territory of the county or counties from which such territory has theretofore been a part. Two of the persons, if such are to be found, shall be opponents and two advocates of the proposed change of line.