There are four possibilities for the offspring of people with blood types A and B. Blood types A, B, AB, and O are possible. Because human blood type is genetically controlled, the child’s blood type is a joint control of the parents’ blood type. in a person with blood type A, there are two expressions of blood group antigens, either two A antigens together or one A antigen and one O antigen together. in a person with blood type B, there are also two possibilities, either two Bs together or one B antigen and one O antigen together. If there are two A antigens together and two B antigens together on the other side, there is only one possibility for the offspring to be AB. If one partner has one A antigen and one O antigen together and the other partner has one B antigen and one O antigen together, there are four possibilities for offspring, including A, B, AB and O blood types.