It could only happen if he got help from Undertaker from the very first time though
I'm so sorry but all the theories like this and the affection of R!Ciel to O!Ciel makes me ship them both so much! I understand if you're disgusted, but it's so cute for me!
Don't be sorry. It's all still unclear what happened to both of them in the past. We only see/read a small fragment of it, like the mansion was on fire, Vincent and Rachel died because of it, R!Ciel has shown dead on the table, and our Ciel has called a demon to save him. If this mystery is solved, I'm afraid we'll see the end of this series except Yana Toboso sensei has something up to her sleeve.
Oh, weird theory tho. What if the real Ciel was the one who planned his whole family's death? Because he didn't want our Ciel to wander off to the real world while he takes over the family business? I mean, this child is really rubbing me off in a wrong way... He's TOO perfect!(〜￣△￣)〜