I heavily theorize/headcanon that the reason Otto became so attached towards Cici is because their parents weren’t present in their lives. Is very likely Cici experienced some type of parentification, where she became Otto’s caretaker.
The implications that Otto suffered from bulling at school and Cici possibly being the one who defended/look after him further supports this.
A constant theme through the game, is all the kids coming from incredible neglectful backgrounds. Is sad, but I can totally see Otto’s parents adopting Cici either for appearance or to give him a playmate, or someone to look after him.
There’s also the implication that she might not be from the same race as Otto’s and the difference in social class implies in Altered Echoes.
Add to this the bulling, the parental neglect and her having to possibly look after and take care of Otto even though she was a kid herself. I don’t think Otto had to be a spoiled or bad kid. He clearly loved her a lot, but her attachment towards her isn’t normal. Which leads me to believe she might have been her primary caretaker/the one who looked after him instead of their parents.
And the reason they didn’t connect even though they cared a lot about each other may have been due the alienation she suffered from her race and social class.
This! I was almost tempted to add the parentification aspect in my original post but yes!
I 100% believe with the way Otto talks about Cici that she was a sort of mother figure to him!
As for the race thing, what you said about alter echos makes me believe you are under the impression that Six is Cici, but six is not the original owner of Cici’s raincoat, it’s a lesser known game but there is a canon mobile game ‘very little nightmares’ were we are introduced to the character ‘raincoat girl’ (photo at bottom) whom i believe may actually be Cici
A character who like Otto shares his brown hair and even has potential hints to Otto’s character long before his introduction (the eyeball hands in the neat courtyard)
However I do agree with you on the prospect that Cici was not white like Otto, because if you do a simple color pick ON RCG’s character she does come up as a darker skintone
This could simply be from shadows, the chosen muted color palette or because Cici IS a different race than Otto’s expired mayonnaise colored ass
there is also a valid argument to be made that cici
A, might’ve been adopted like you suggested
B, is mixed race, potentially even a child from a previous marriage of one of Otto’s and her’s own parents
Which COULD explain why she was potentially subjected to different treatment than Otto if she was a child from a different marriage (or maybe even an affair baby???)
This could explain why Cici was neglected like we see with the other children, carrying on those same themes we see in Little nightmares
It’s clear Cici endured some sort of neglect/mistreatment that Otto did not face otherwise it’s very likely Otto would’ve ALSO been snatched when he was a child but perhaps while their parents were overall absent before, Cici’s disappearance caused them to put more effort into Otto as a whole
Possibly even coddling him which could aid in his already traumatized mind from Cici’s disappearance to become more twisted
No matter the Case of Cici and Otto’s childhoods it’s clear Otto grew a very unhealthy attachment towards his sister and viewed her more as a mother figure than a simple older sister, aiding to her potentially being parentified if it wasn’t only her parents but Otto (unknowingly) parentifying her
It is my belief that Cici and raincoat girl are one in the same
Not only is raincoat girl the first child we see WITH the raincoat
Likely gaining it from the circus where it was in the possession of the perfect lady and then crash landing into the nest
But she shares the same hair color as Otto & like I said the hints to Otto’s nowhere variant (the hypnosis) and the hands with eyes
(Bonus to cici/raincoat girl being darker skinned when you compare her to the pretender in the end scene she is noticeably darker)