The HBP (or more likely How to Discredit all my future theories!!)

[halli]

No: HPFGUIDX 105505

-griffyr29:
> We know that V's mother died giving birth to him, but we know 
> little else about her other than that she was a witch. Perhaps
> she had children in a previous marriage. That would make those 
> children "half-blood" (in the more Muggle sense) relatives of V. 
> 
> I'm also thinking that Snape would fit in nicely as a descendant.


halli:
   Well, the only problem with this idea is that if VM had any half-
siblings on his mothers side, they would also be desendants of 
Slytherin, as that was on his mother's side. DD said that VM was the 
last remaining desendant so that wouldn't work. Unless DD doesn't 
know about them, but you would think he would look into something 
that important.