The twin theory is true.
It’s a matter of time this came to light. There were many hints’ given. I don’t remember each one of them right now but there were clues.
In the circus arc(?) in Ciel’s memory, we see one of the twin hiding behind Vincent and the other happily greeting the guests. The time when the Phantomhive mansion was burned Ceil was abducted, we saw two of them. One was caged and the other was on the ritual table. How did he survive? Maybe Ciel thought he died, he’s in too much pain and agony and wanted to leave. The devil came, Ciel made a pact, took his revenge and never looked back.
Why didn’t Elizabeth her parents or brother ever talked about the other twin? In one of the chapters Ciel says that he doesn’t lie and Sebastian snickers at the statement. Does that mean Sebastian knew about the twin? Ciel’s shaking when he read “who stole the candy from my tummy?” written on the wall.
We all know Souma was very happy to see the person who entered. It’s obvious he knew that person but Agni suspected something after going through the fireplace. He found a picture, maybe it’s a picture of two Ciel. We all know what happened to Agni. And now Souma thinks its Ciel who killed Agni. My friendship!!
In Ciel’s gang, Finny’s the first one to notice that their young master looks different. Why only him?
The twin introduces himself as the head of the Phantomhive, Ciel Phantomhive. He looks like Vincent and I believe he’s the real Ciel.
But why did the other Ciel took this name? What is his name? Why does he look scared to see the twin? He knew the other twin’s coming that’s why he told Sullivan not to open the door not even for him and then he told Sebastian he wants to confirm something and went straight to his mansion. Why did the real Ciel appear now? Where’s he all this time? Why did he kill Agni? Why is he being referred as a Blue star? Did Elizabeth ran away because she knew the truth?