I think what he's saying is that the phonebook on his SonyEricsson W995 has become corrupted. In particular, the entry for his brother's phone number has been overwritten by the phone number of the person immediately preceding in alphabetical order.
Unfortunately, this sort of memory corruption is well known in SonyEricsson handsets. The handset will need a master reset and to have the firmware reflashed. If there is no existing backup (why?) then the contacts will need to written down beforehand and entered again manually afterwards,