I've noticed that some threats are so short, that they end up quickly or we finish in something else, so I decided to make this one general; and because I'm going to explian my theory about each of the heir's the subject is perfect (okay too much explanation, lets go to the point)
Each of the houses must have a heir (even if some house is more important than other); so I thought that we already know Slytherin's, and must of us agree the HArry theory about being the GG' one is very probable (we like it not); so I just thought that there must be in some part also heir's of Ravenclaw and Hufflepuff; I thought that Susan Bones could be the one from Hufflepuff, since his parents were also killed by Voldemort. About Ravenclaw's I'll think later in that one; any maybe this wizards are the order of the phoenix, where only selected witches and wizards are allow to enter.