Another candidate for RAB

[Arley Dotinei]

No: HPFGUIDX 150999

    eggplant: 
<snip> So RAB must be a member of the Black family with a first name 
that starts with an R, I can't think of anybody who fits that bill 
except Regulus, besides I can't imagine why JKR would introduce us to 
a character like Regulus unless she had need of him in a later book. 
As for his middle name I would guess Arcturus or Aldebaran or Altair 
or Antares. 

  Arley: 
I agree with you, RAB is definitely a Black and Regulus is the most 
likely candidate. But why couldn't it be Aunt Andromeda? If her full 
nome was something like Regina Andromeda Black (my guess, not suggested 
anywhere in the books), it could be. But it would be a long shot. For 
everything we know about Regulus, I'm almost sure it's him.
   
  cheerio