In such a case, according to the rules of blood group inheritance: A + A → A, O; A + B → A, B, O, AB; A + O → A, O; A + AB → A, B, AB; B + B → B, O; B + O → B, A, AB; O + O → O; O + AB → A, B; AB + AB → A, B, AB. From the rules listed above, as long as there are no parents with AB situation, then the offspring will have the blood type O.