I haven't fully caught up to the manga but I was wondering how you can tell which is our ciel and which is the real ciel in the flashbacks when they're children?
There are several ways to tell! We figure out what boy is which by going through the set of criteria and seeing who fits best, it isn’t always obvious what twin we’re looking at though.
- Confident and outgoing, seen as “mischievous” by Pit.
- Never had asthma.
- The heir to the Phantomhive name.
- Usually seen being close to Madam Red or Lizzy.
- When kidnapped, has a dark bruise under his left eye.
- When kidnapped, has no broken buttons on his shirt.
- Will be addressed as “Ciel” by others.
- Will be addressed as “Lord Ciel” by Tanaka.
- Is killed on the altar.
- Hair usually swishes to our
- Shy and quiet, scared to speak to strangers and is seen as “frail” by Vincent.
- Had debilitating asthma, had to undergo a “medical recuperation”.
- Not the heir to the Phantomhive name.
- Never addressed as “Ciel” aside from when translation errors occur.
- Addressed as “Young Master” by Tanaka.
- Usually seen with Tanaka as opposed to Lizzy or Madam Red.
- Usually seen inside the Phantomhive manor.
- When kidnapped, has no dark bruise under his eye.
- When kidnapped, has a broken button on his shirt.
- Does not leave the cage until after meeting Sebastian.
- Hair usually swishes to our right.
NOTE: the hair direction is not always 100% consistent, however they are “mirror twins” as confirmed by Yana so it’s mostly accurate!
So there is a lot to choose from. But these are the things I consider when trying to work out who is who, it’s mostly successful! The only time that we’re not completely certain about is this instance here, but even then the hair-partings hold up so I agree with @akumadeenglish in their post linked.