Alot of the time in FMH2010 I sign Edinson Cavani and Luis Suárez who are both Uruguayan. They both always get called up to the Uruguay squad for the World Cup in 2010 but then whilst playing as Manchester city I noticed that only Suarez got called up to the Uruguay squad despite Cavani scoring 26 goals for me that season, Then the following day I got a msg saying that Cavani had been called up to the ITALY squad for the world cup !! His nationality was
So he he was then declared as Italian. I found this strange and Started a new game as the Italian manager but I was not able to select Cavani or any other player with duel Italian / An Other nationality !
If it is similar to the PC version(which I guess it is). It could be to do with the manager of the Italian national side before you. Also some players may have dual nationlaity but they may only be interested in playing for 1 national team at a certain stage. This can change though if player X doesnt get called up after a few years by the national team he wanted to play for.
It can happen irl also - basically each country in the world has different rules upon obtaining their nationality.
For instance I've lived in America for around 3 years now, I believe I'll be elligable for becoming a 'citizen' shortly if I decide to pass the relevant tests etc. required to do so.
After that if the American national team were REALLY desperate (and England don't see sense and call me up before then ;) ) I could play for them
It happens rarely irl because (1) people tend to be reasonably patriotic, (2) generally players only move to a nation once they're relatively mature and thus if good enough to obtain national caps they've already done so.
One 'interesting' real-life case might have been Kasper Schmeichal (son of ex-Man Utd/Man City player) - from his wikipedia page he had the chance to play for both England and Denmark: Following his strong showings for Manchester City in the early 2007–08 season, it was reported on 23 August 2007 that The Football Association were investigating Schmeichel's international status, to see if there was any chance of him foregoing his Danish international status in order to play for the England national football team. However, Schmeichel stated that he would only ever play for Denmark.