My mum blood group is IAIO, my father is blood group is IOIO, is it possible my blood group is AB?

It is quite possible for children to have a different blood type from their parents, even if both parents have the same blood type. For example, if both parents are type B and have the BO antigens, they could have children who are BB (B antigen inherited from both parents), BO (B from one parent, O from the other) or OO (O antigen from both parents). This makes analysis of blood types sound very simple but if antigens other than those in the ABO system are looked at, the picture may become morecomplicated. At least nine major and 24 minor antigen systems are now recognised so if these are also analysed it might show that individuals who have the same ABO blood type have numerous differences with regard to other antigens. I hope this answers your query!