(1) Class A: Husband, wife, son, daughter, lineal ancestor, lineal descendant, brother, sister, stepchild, son-in-law or daughter-in-law. If a person has no child or grandchild, a niece or nephew of such person and the issue of such niece or nephew shall be a donee within this class. For the purposes of this part, a person who is related to the donor as a result of legal adoption shall be considered to have the same relationship as a natural lineal ancestor, lineal descendant, brother, sister or stepchild; and
(2) Class B: Any other relative, person, association or corporation not specifically designated in Class A.