Question

Mary has type A blood and her husband (John) has type B blood. John's parents both had type AB. Mary and John have three children, one with type A, one with type AB, and one with type B. Relatives suspect that one of the children was adopted.

Answer 1

Type B would be adopted, it just doesn't work with the phenotype.

Answer 2

None of the children are adopted just one of the them got both of there parents blood types