Yeah, so in order for this theory to work Sirius could have never died.
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I really think Sirius is dead,Why would JKR want Sirius 2 come back?
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Sirius was not hit by the avarda kadarva [wrong spelling ?] every other time this spell is used she clearly states that the spell was green in this case she wrote P805Bottem
"Come on you can do better than that" he yelled as a second jet hit him squarely in the chest the laghter had not quit died from his face but his eyes widened in shock.
at witch piont Harry trys to go get him if he was hit by the killing curse then Harry would have known that he was deda like w Dombeldore when he is beleved to be killed
We know Dombeldore did not die right club

JKR also said on her page that the mirror that Sirius Gave Harry will have somthing to do in the next book
mabe that is how he directs harry to bring him back