People with blood type B and AB have children with three blood types: one with blood type A; one with blood type B; and one with blood type AB, with no blood type O. Because human blood types are genetically controlled by the parents, a person with blood type B can only provide two possibilities, an antigen of blood type B and an antigen of blood type O. A person with blood type AB can provide an antigen of blood type A and an antigen of blood type B. A person with blood type B can provide an antigen of blood type A and an antigen of blood type B. A person with blood type AB can provide an antigen of blood type A and an antigen of blood type B. If the antigen of blood type O and the antigen of blood type A are together, the child is blood type A. If the antigen of blood type O and the antigen of blood type A are together, the child is blood type A. If the antigen of blood type O and the antigen of blood type B are together, the child is blood type B. If the antigen of blood type B and the antigen of blood type A are together, the child is blood type AB. if the antigen of blood type B and the antigen of blood type B are together, the child is blood type B. if the antigen of blood type B and the antigen of blood type B are together, the child is blood type B. Therefore, a child born to a person with type B blood and type AB blood can only be type A, type B or type AB.