I think it's him, I never believed him to be dead for some reason.
It all fits I think. I mean, what would the point in introducing a new character; who is related to Sirius and was ment to be a Death Eater and is supposedly dead for the sole purpose in filling up one or two lines on a page?

The answer: none.

One thing though about D.dore I think he really is dead because it fits well with the whole 'Fighting for what you think is right' Philosophy that he had going on. The Christianity brigade would attack J.K down with pointy sticks if she somehow brought him back to life.
I know its a story but it'd be too long winded if she decided to bring him back. Know what I mean?

 

But what would the point be in making up a character, with no apparent (as of yet) reason to him existing other than him to serve a porpose later on?
This is getting a little repetitive isn't it?
Let's just wait and see, shall we.

 

Bah, im done with these theories. I tried Rudolphus(jHow do you spell his name!?) and Bella, and instantly ruled it out. No one has those initials. Its got to be something I missed.... Im almost sure the A is and. A former DE.... Maybe Lily knew something about it? The note said it was a former death eater who died afterwards... Maybe the letters are initials rearanged? The reason JKR didnt answer the question of 'can we determine this with our knowledge of books 1-6' is because it probably was Regulus..

 

Ruldolphous or Rabastan, Andromeda, Bella.