tom riddle and voldemort are the same person are they not?! tom is a yonger version of voldemort preserved in a diary. and JK said it was not Harry or Voldmort.

could it be Draco malfoy? tho hes not half blood so mayb not!!

it couldn't be dobby because hes not even a wizard and i don't think you can be a half - blood house-elf!! i cannot think of any other half - bloods in the book unless it is a very minor character.