I think that the nationality of the parents is what defines his nationality not where he was born and you have to remember that when he was born it was Yugoslavia. In games they always say that he is a Croat - but sometimes they also say his name wrongly so maybe that is not proof. As for the language there is still conflict over where or not they should be called Serbian and Croatian or Serbo-Croat (although most linguists now agree that they are seperate languages) but there is no official language called Bosnian. If he moved around a lot there will probably be elements of both languages in his speech but his grammar will probably come from where ever he did his highest level of education. That would be Croatia I think. Unless there is some Croat/Serb/Bosnian on the board who could tell you which accent he has.