I reckon that Sirus' brother was the "R.A.B.", and i don't know about wether or not Snape's evil...i want to know if anyone else is suspicious about Slughorn; where was he during Dumbledore's death? I know he was mentioned when he was asked to call the minstry, and act as the head of Slitherin, but where was he before that???
Luckily I've already read the book so you haven't ruined it for me... but it was pretty selfish of you not to put a spoiler warning up. Please consider the enjoyment of other users in future questions.
Don't worry. I didn't mean to reply to what may have been your first ever question, by having a go at you. But it's been mentioned before (prob before you joined) about declaring spoilers!
I certainly thought it was Regulus. And if you go onto www.mugglenet.com and look at their interview with JK Rowling (which is in three parts), you'll see that they say "we think it's Regulus" and she says (can't remember exactly) something along the lines of "that would be a fine answer".
I have a thought about snape being evil - well actually my mum does! She says she thinks snape killed dumbledore to save him because he drank that nasty potion!! I cant decide if i think this a good idea or utter tosh and snape is a double crossing fiend!! What do you think??
Incidentally, if you remember from book 5, when they were cleaning out 12 Grimmauld Place: one of the things they found was a heavy locket that none of them could open... then Kreacher kept rescuing things from the bin that his mistress wouldn't want to see thrown away... then Mundungus burgled the house once Kreacher was gone... just a thought!
Remember that Slughorn is a slitherin. Whether or not Snape is evil or not, but he killed Dumbledore, who trusted him. If Dumbledore didn�t know about Snape to turn on him ( I don�t know about that, I personally think Dumbledore "told" Snape to kill him to keep his cover ) but if he didn�t know and trusted Snape, then perhaps he mistrusted Slughorn as well. Who knows what he could have done while everyone else was fighting. He could have helped the Death Eaters after all......