ตอนแรกก็ไม่คิดว่าจริงหรอก แต่พอไปอ่านนอกบอร์ดนอกมา อืม เริ่มคล้อยนิดๆค่ะ
จากนี้ค่ะ: cr.http://forums.blackbutler.net/showthread.php?8012-The-Two-Ciels-Theory-V2
สรุปกันได้มันมาก อ่านตาเปียกตาแฉะ

คิดว่ายังไงบ้างคะ?
รวมข้อมูลประกอบ
[Spoil] คลิกเพื่อดูข้อความที่ซ่อนไว้
The 2CT supposes there being two physical Ciels, probably twins:
Older brother (real Ciel Phantomhive)
- the cheerful and bright boy who we see in flashback scenes
- rightful heir to the Phantomhive house, Lizzy's fiance
- stabbed to death by cultists on the sacrifice altar
- we see him in these flashbacks: Ch10 Ch31 Ch34 Ch58

Younger brother (current Ciel Phantomhive)
- our bratty Young Master
- had bad asthma in his childhood
- survived and made contract with Sebastian
- took on the identity of his brother for whatever reason
- we see him in these flashbacks: Ch28 Ch31 Ch40 Ch58

And we see both of them in:
Kelvin's flashback
Ciel's flashback Ch54 Ch90
Side Story "That butler, nursing" (p7-22 real Ciel and p23-25 our Ciel)

---

So,
As you all know the original Kuroshitsuji is written in Japanese, which is a really complicated and ambiguous language. So it's very difficult to translate it properly and very easy to make mistakes even for professional translators. Here are two things you should keep in mind about translation:

grammatical/linguistic problem
*In Japanese language the singular and plural forms of a noun are completely identical.* The only way to distinguish singular/plural is using a "plural marker"-suffix, which clarifies that the number of people in question is more than one. That means, unless they add this plural-suffix, it's always open whether the characters are talking about one or more persons. Yana usually makes it so that both interpretations are possibl are some examples:
Ch.10 English: "It's going to be my son's 10th birthday soon!" -> original: "It's going to be my son's/sons' 10th birthday soon!" (singular/plural not specified)
Ch.11 English: "There was no sign of their child's body." -> original: "There was no sign of their child's/children's body/bodies."
Due to this characteristic of Japanese, it was never confirmed that Ciel was an only child (if anything, it's more or less confirmed that he had siblings) in the original version of the manga, whereas in the English version Ciel is always portrayed as an only child.
[Spoil] คลิกเพื่อดูข้อความที่ซ่อนไว้It is VERY easy for a translator to make mistakes, especially in Japanese which is ambiguous by design and thus requires a lot of context to understand. Take note that a translator translates a passage as he/she understands it, which means that whenever you read a manga in English, you are reading through the glasses of somebody else. A translation is a kind of censorship. The way they interpreted the dialogue will be the way you will understand it, even if it's not what the original author intended.

---

Possible interpretation and hints based on twins theory
*To avoid confusion, I'll refer to our Ciel as "Young Master"YM).
*Remember: It's just one possible way to interpret the scenes. Of course, there can be other interpretations.
*The list below is based on the original manga. That's why the lines sometimes differ from the online English version.

Ch.2
p10 YM calls Lizzy "Elizabeth" instead of "Lizzy". (cf. Ch. 58)
p33 "The head of the Phantomhive house is me, "Ciel Phantomhive""
-> Why is his name put in quotation marks?
p40 "How many times has this ring witnessed the death of its master? Grandfather... father... and..."
-> Whoelse's death did the ring witness?
p41 "When I close my eyes I can hear that death scream"
-> YM is referring to a specific death scream, probably that of real Ciel as he(YM) witnessed from the cage how he got stabbed to death.
p43-44 Sebastian recalls the scene in which YM claims that he is 'Ciel', the head of the Phantomhive family, and smirks at it.

Ch.4
p33 "The sacrifice that was offered... and the happiness you left behind you." (Sebastian)
-> sacrifice = real Ciel's death

Ch.8
p23 three graveyards (cf. Ch.62)
-> See Q&A in my post below

Ch.10
p9 "Should I take the ring out?" (Sebastian)
-> Take the ring out from what? (Crack theory: Sebastian took out the blue ring from real Ciel's dead body right after he was summoned.) See Q&A below.
p30-31 "It's a boy/ They are boys" (nurse) -> *sigular/plural not specified
-> this birth scene can be interepreted as there being two babies (one lying beside Rachel, the other one hold by Angelina)
p33 "My cute nephews" (Madam Red) -> *plural used in original language

^{*かわいい=cute　甥っ子=nephew/nephews　達=plural-suffix => 'my cute nephews (definitely plural)'}

p35 "It's going to be my son's/sons' 10th birthday soon!" (Rachel) -> *singular/plural not specified

Ch.11
p4 "There was no sign of their child's/children's body/bodies" (Madam Red) -> *singular/plural not specified
*Side note: The official Spanish version translated the same sentence: "The bodies of the children weren't found".

Ch.13
p18　"I knew there was a chance of saving her. I knew that I would let that chance slip away. I kept that in mind and let her die. Even my own relative." (YM)
-> YM could be referring to his brother too.
p28　"Madam... she can not kill me, Ciel,... her own relative." (YM)
-> YM again puts the emphasis on the name "Ciel".

Ch.14
p22 "Aunt Anne loved Ciel most among us." (Lizzy)
-> Weird wording: If there were only Lizzy and Ciel, Lizzy would have rather said: "She loved Ciel more than me."

Ch.17
p34 "They won't return no matter how much I try" (YM)
-> panel shows Vincent, Rachel, real Ciel, Sebastian(the dog), Madam Red, all those precious people who YM lost

Ch.19
p6 "Ciel-sama is... It's too cruel for you!" (Tanaka)
-> There's a translation inaccuracy in the online English version. In the original manga it seems more like "Ciel-sama" and the person who Tanaka is talking to are NOT the same person, i.e. Tanaka tried to say something about Ciel (like "Ciel-sama got kidnapped/ is injured/ etc) and didn't/couldn't complete his sentence to the end because either he was totally confused or it would have been "too cruel" for YM to accept.
The only fact we get to know from this scene is that Tanaka used to call Ciel 'Ciel-sama', but since the day YM returned back accomponied by Sebastian he calls him 'young master'.
p7 "It's rare, huh?"/"This is worth more than 2 people!" (kidnappers) -> might be referring to the twins
p7 "And you, let me give you the mark of a noble beast."
-> It's difficult to translate it in English but the particle used in the original languag implies that the occultist or whoever said that line is comparing Ciel with someone else: 「お前には崇高な獣の印をあげようね」
p9　"Why... Why us?" (YM)　
p11 "You have summoned me. (...) What has been sacrificed will never be returned. Now choose." (Sebastian)
-> *Note: The sacrifice had been made before YM made the contract with Sebastian. So the sacrifice that summoned Sebastian (real Ciel's soul) and the sacrifice to conctract with the demon (YM's soul) are two different things.

Ch.28
p10-11 "Humans have no scruples about lying. Myself included." (YM) -> might be referring to his own false identity

Ch.29
p12 "Young Master certainly has a lot of lies and secrets." (Sebastian)
p14 panel bottom left shows the real Ciel-greets-Kelvin-scene from YM's perspective (cf. Ch.31-32)
*Translation inaccuracy:
Online version: "But I did greet him at some parties my predecessor took me to."
Original version: "I'm not sure but I think I at least greeted him once at some parties my predecessor took me to..."

Ch.31-32 Kelvin's flashback scene, detailed explanation here
*Possible interpretation: There are two boys at the party, the cheerful boy who greeted Baron Kelvin and the shy boy who hid behind Vincent:
Vincent's right or left side is always hidden by something and his posture suggests that there might be a second child:


และมันยังอีกยาวมาก อ่านต่อได้ที่ http://forums.blackbutler.net/showthread.php?8012-The-Two-Ciels-Theory-V2
Info 1