okay well im sorry but heres the thing. if JK was originally going to name CoS, HPB then there is no way that the half blood prince can be anyone besides Tom Riddle. yes justin would be a good candidate as would hagrid as would a series of other characters but the truth of the matter is that none of the characters that have been suggested as possible half blood princes play significant enough roles n the 2nd book for it to be named after them besides Tom Riddle. am i wrong? i have carefully considered the different options that have been posted here and have come to the conclusion that there is no other possible half blood prince. however, if the content of CoS was altered at the same time that the title was changed then any number of characters, known and unknown are good possibilities as the half blood prince. what do you think?