• The Peverells have to count for something. At least, it seems like they should if JKR bothered to name them.
   
  
• The rings seen in OotP and HBP seem to suggest, at minimum, that the Gaunts and Blacks were at one time part of a similar class or group of families. And if they were both pureblood with similar attitudes about staying pureblood (likely, given what we saw of Walburga and Marvolo), what are the odds they didn't intermarry?
   
  
• The Black Family Tree doesn't go back nearly far enough to make this unlikely. Here's an example of one way the Peverells, Blacks, and Gaunts could be related (look at the magenta section, and remember you can zoom in on .swf files). There's lots of ways you could work it, and it's fairly easy to set it up so that only the Gaunts are descendants of Slytherin. You can even add extra drama by doing things like having a widow Peverell with children remarry a Black and have children with him. Even though the Black children are younger, they'd still get the inheritance because of their last name. Peverell angst!
   
  
• Merope's name is a star name. It works for the "married a mortal" story, of course, but it's also a star. (In some versions of the story that I am too spoiler-phobic to find a link to right now, Merope is the star you can't see.) Her name could've come from an ancestor. The Blacks reuse the same star names over and over.
   
  
• Number 12 Grimmauld Place has a decorative snake on the door. Morfin nailed a snake to the door of the Gaunt's house. Okay, Morfin's crazy. But still, the snake on the Gaunt's door was mentioned repeatedly in that scene. It even had a poem. And it makes the Gaunts' shack a sad parody of the House of Black. (So does the chapter title, by the way.)
   
  
• It would mean there was all the more reason Regulus Black was able to discover Voldemort's secret. The secret being, as it turns out, that the Dark Lord was actually a lowly half-blood.
   
  
• It might relate to Orion's death in the same year as Regulus'. Hepzibah Smith told Tom M. Riddle the story of how Burke bought the locket off of Merope for a pittance when she was pregnant and alone in London. The readers already knew about that, so I've wondered if that's a setup for us to discover that Voldemort later killed Burke as some kind of revenge. (My guess is that Burke's dead because of the way Dumbledore phrased his sentence about Burke's generosity. But I don't think that's a canon fact.) This is a total shot in the dark, but what if Merope was in London with no family to go home to and decided to stop by her relatives' house? Poor, squib-ish, and pregnant with a Muggle's baby, the Blacks would certainly have turned her away. If Voldemort was later murdering people who messed with his mom, he could've gone after the Blacks as well. Yes, I know Orion wasn't old enough to have been the one to send Merope away. No, I don't have a clear-cut reason why Voldemort would've targeted him. Like I said, shot in the dark. But if it's something close to the truth, it would've given Regulus an even stronger incentive to turn on Voldemort.

There you have it, a big mess of pseudo-clues. You can tell I'm getting down to the dregs, here. Only one more theory left that I'd like to try to post and it's kind of a doozy. I hope I have time.

Oh, and here's my version of the Black Family Tree without the made-up junk on it. I've got a nice, printable copy, too. I meant to post that one before we went into spoiler lockdown, but never got around to it. I'll put it up sometime after the book release (possibly with edits, if we learn a certain someone's middle name, etc.). I expect it might be useful for fanfic writers or something.